diff --git a/src/Locator/SanitizeLocator.php b/src/Locator/SanitizeLocator.php
index 22ba36c9..60f9c738 100644
--- a/src/Locator/SanitizeLocator.php
+++ b/src/Locator/SanitizeLocator.php
@@ -37,6 +37,9 @@ protected function initFactories(array $factories)
             'between'               => function () { return new Sanitize\Between(); },
             'bool'                  => function () { return new Sanitize\Boolean(); },
             'callback'              => function () { return new Sanitize\Callback(); },
+            'caseLower'             => function () { return new Sanitize\CaseLower(); },
+            'caseTitle'             => function () { return new Sanitize\CaseTitle(); },
+            'caseUpper'             => function () { return new Sanitize\CaseUpper(); },
             'dateTime'              => function () { return new Sanitize\DateTime(); },
             'field'                 => function () { return new Sanitize\Field(); },
             'float'                 => function () { return new Sanitize\Double(); },
diff --git a/src/Locator/ValidateLocator.php b/src/Locator/ValidateLocator.php
index 8bd5430c..f6fdce5c 100644
--- a/src/Locator/ValidateLocator.php
+++ b/src/Locator/ValidateLocator.php
@@ -37,6 +37,9 @@ protected function initFactories(array $factories)
             'between'               => function () { return new Validate\Between(); },
             'bool'                  => function () { return new Validate\Boolean(); },
             'callback'              => function () { return new Validate\Callback(); },
+            'caseLower'             => function () { return new Validate\CaseLower(); },
+            'caseTitle'             => function () { return new Validate\CaseTitle(); },
+            'caseUpper'             => function () { return new Validate\CaseUpper(); },
             'creditCard'            => function () { return new Validate\CreditCard(); },
             'dateTime'              => function () { return new Validate\DateTime(); },
             'email'                 => function () { return new Validate\Email(); },
diff --git a/src/Rule/AbstractCharCase.php b/src/Rule/AbstractCharCase.php
new file mode 100644
index 00000000..5c792de5
--- /dev/null
+++ b/src/Rule/AbstractCharCase.php
@@ -0,0 +1,91 @@
+<?php
+/**
+ *
+ * This file is part of Aura for PHP.
+ *
+ * @license http://opensource.org/licenses/bsd-license.php BSD
+ *
+ */
+namespace Aura\Filter\Rule;
+
+use Aura\Filter\Exception;
+
+/**
+ *
+ * Abstract rule for character case filters; supports the `mbstring`
+ * extension.
+ *
+ * @package Aura.Filter
+ *
+ */
+abstract class AbstractCharCase
+{
+    /**
+     *
+     * Is the `mbstring` extension loaded?
+     *
+     * @return bool
+     *
+     */
+    protected function mbstring()
+    {
+        return extension_loaded('mbstring');
+    }
+
+    /**
+     *
+     * Proxy to `mb_convert_case()` when available; fall back to
+     * `utf8_decode()` and `strtolower()` otherwise.
+     *
+     * @param string $str String to convert case.
+     *
+     * @return string
+     *
+     */
+    protected function strtolower($str)
+    {
+        if ($this->mbstring()) {
+            return mb_convert_case($str, MB_CASE_LOWER, 'UTF-8');
+        }
+
+        return strtolower(utf8_decode($str));
+    }
+
+    /**
+     *
+     * Proxy to `mb_convert_case()` when available; fall back to
+     * `utf8_decode()` and `strtoupper()` otherwise.
+     *
+     * @param string $str String to convert case.
+     *
+     * @return string
+     *
+     */
+    protected function strtoupper($str)
+    {
+        if ($this->mbstring()) {
+            return mb_convert_case($str, MB_CASE_UPPER, 'UTF-8');
+        }
+
+        return strtoupper(utf8_decode($str));
+    }
+
+    /**
+     *
+     * Proxy to `mb_convert_case()` when available; fall back to
+     * `utf8_decode()` and `ucwords()` otherwise.
+     *
+     * @param string $str String to convert case.
+     *
+     * @return int
+     *
+     */
+    protected function ucwords($str)
+    {
+        if ($this->mbstring()) {
+            return mb_convert_case($str, MB_CASE_TITLE, 'UTF-8');
+        }
+
+        return ucwords(utf8_decode($str));
+    }
+}
diff --git a/src/Rule/Sanitize/CaseLower.php b/src/Rule/Sanitize/CaseLower.php
new file mode 100644
index 00000000..3ca9a664
--- /dev/null
+++ b/src/Rule/Sanitize/CaseLower.php
@@ -0,0 +1,42 @@
+<?php
+/**
+ *
+ * This file is part of Aura for PHP.
+ *
+ * @license http://opensource.org/licenses/bsd-license.php BSD
+ *
+ */
+namespace Aura\Filter\Rule\Sanitize;
+
+use Aura\Filter\Rule\AbstractCharCase;
+
+/**
+ *
+ * Sanitizes a string to lowercase.
+ *
+ * @package Aura.Filter
+ *
+ */
+class CaseLower extends AbstractCharCase
+{
+    /**
+     *
+     * Sanitizes a string to lowercase.
+     *
+     * @param object $subject The subject to be filtered.
+     *
+     * @param string $field The subject field name.
+     *
+     * @return bool True if the value was sanitized, false if not.
+     *
+     */
+    public function __invoke($subject, $field)
+    {
+        $value = $subject->$field;
+        if (! is_scalar($value)) {
+            return false;
+        }
+        $subject->$field = $this->strtolower($value);
+        return true;
+    }
+}
diff --git a/src/Rule/Sanitize/CaseTitle.php b/src/Rule/Sanitize/CaseTitle.php
new file mode 100644
index 00000000..eda84a5f
--- /dev/null
+++ b/src/Rule/Sanitize/CaseTitle.php
@@ -0,0 +1,42 @@
+<?php
+/**
+ *
+ * This file is part of Aura for PHP.
+ *
+ * @license http://opensource.org/licenses/bsd-license.php BSD
+ *
+ */
+namespace Aura\Filter\Rule\Sanitize;
+
+use Aura\Filter\Rule\AbstractCharCase;
+
+/**
+ *
+ * Sanitizes a string to title case.
+ *
+ * @package Aura.Filter
+ *
+ */
+class CaseTitle extends AbstractCharCase
+{
+    /**
+     *
+     * Sanitizes a string to title case.
+     *
+     * @param object $subject The subject to be filtered.
+     *
+     * @param string $field The subject field name.
+     *
+     * @return bool True if the value was sanitized, false if not.
+     *
+     */
+    public function __invoke($subject, $field)
+    {
+        $value = $subject->$field;
+        if (! is_scalar($value)) {
+            return false;
+        }
+        $subject->$field = $this->ucwords($value);
+        return true;
+    }
+}
diff --git a/src/Rule/Sanitize/CaseUpper.php b/src/Rule/Sanitize/CaseUpper.php
new file mode 100644
index 00000000..b881fb74
--- /dev/null
+++ b/src/Rule/Sanitize/CaseUpper.php
@@ -0,0 +1,42 @@
+<?php
+/**
+ *
+ * This file is part of Aura for PHP.
+ *
+ * @license http://opensource.org/licenses/bsd-license.php BSD
+ *
+ */
+namespace Aura\Filter\Rule\Sanitize;
+
+use Aura\Filter\Rule\AbstractCharCase;
+
+/**
+ *
+ * Sanitizes a string to uppercase.
+ *
+ * @package Aura.Filter
+ *
+ */
+class CaseUpper extends AbstractCharCase
+{
+    /**
+     *
+     * Sanitizes a string to uppercase.
+     *
+     * @param object $subject The subject to be filtered.
+     *
+     * @param string $field The subject field name.
+     *
+     * @return bool True if the value was sanitized, false if not.
+     *
+     */
+    public function __invoke($subject, $field)
+    {
+        $value = $subject->$field;
+        if (! is_scalar($value)) {
+            return false;
+        }
+        $subject->$field = $this->strtoupper($value);
+        return true;
+    }
+}
diff --git a/src/Rule/Validate/CaseLower.php b/src/Rule/Validate/CaseLower.php
new file mode 100644
index 00000000..c5f1ff24
--- /dev/null
+++ b/src/Rule/Validate/CaseLower.php
@@ -0,0 +1,42 @@
+<?php
+/**
+ *
+ * This file is part of Aura for PHP.
+ *
+ * @license http://opensource.org/licenses/bsd-license.php BSD
+ *
+ */
+namespace Aura\Filter\Rule\Validate;
+
+use Aura\Filter\Rule\AbstractCharCase;
+
+/**
+ *
+ * Validates that the string is all lowercase.
+ *
+ * @package Aura.Filter
+ *
+ */
+class CaseLower extends AbstractCharCase
+{
+    /**
+     *
+     * Validates that the string is lowercase.
+     *
+     * @param object $subject The subject to be filtered.
+     *
+     * @param string $field The subject field name.
+     *
+     * @return bool True if valid, false if not.
+     *
+     */
+    public function __invoke($subject, $field)
+    {
+        $value = $subject->$field;
+        if (! is_scalar($value)) {
+            return false;
+        }
+
+        return $this->strtolower($value) == $value;
+    }
+}
diff --git a/src/Rule/Validate/CaseTitle.php b/src/Rule/Validate/CaseTitle.php
new file mode 100644
index 00000000..8d485c97
--- /dev/null
+++ b/src/Rule/Validate/CaseTitle.php
@@ -0,0 +1,42 @@
+<?php
+/**
+ *
+ * This file is part of Aura for PHP.
+ *
+ * @license http://opensource.org/licenses/bsd-license.php BSD
+ *
+ */
+namespace Aura\Filter\Rule\Validate;
+
+use Aura\Filter\Rule\AbstractCharCase;
+
+/**
+ *
+ * Validates that the string is all title case.
+ *
+ * @package Aura.Filter
+ *
+ */
+class CaseTitle extends AbstractCharCase
+{
+    /**
+     *
+     * Validates that the string is title case.
+     *
+     * @param object $subject The subject to be filtered.
+     *
+     * @param string $field The subject field name.
+     *
+     * @return bool True if valid, false if not.
+     *
+     */
+    public function __invoke($subject, $field)
+    {
+        $value = $subject->$field;
+        if (! is_scalar($value)) {
+            return false;
+        }
+
+        return $this->ucwords($value) == $value;
+    }
+}
diff --git a/src/Rule/Validate/CaseUpper.php b/src/Rule/Validate/CaseUpper.php
new file mode 100644
index 00000000..5d177de4
--- /dev/null
+++ b/src/Rule/Validate/CaseUpper.php
@@ -0,0 +1,42 @@
+<?php
+/**
+ *
+ * This file is part of Aura for PHP.
+ *
+ * @license http://opensource.org/licenses/bsd-license.php BSD
+ *
+ */
+namespace Aura\Filter\Rule\Validate;
+
+use Aura\Filter\Rule\AbstractCharCase;
+
+/**
+ *
+ * Validates that the string is all uppercase.
+ *
+ * @package Aura.Filter
+ *
+ */
+class CaseUpper extends AbstractCharCase
+{
+    /**
+     *
+     * Validates that the string is uppercase.
+     *
+     * @param object $subject The subject to be filtered.
+     *
+     * @param string $field The subject field name.
+     *
+     * @return bool True if valid, false if not.
+     *
+     */
+    public function __invoke($subject, $field)
+    {
+        $value = $subject->$field;
+        if (! is_scalar($value)) {
+            return false;
+        }
+
+        return $this->strtoupper($value) == $value;
+    }
+}
diff --git a/tests/Rule/CharCaseTest.php b/tests/Rule/CharCaseTest.php
new file mode 100644
index 00000000..5e05ba78
--- /dev/null
+++ b/tests/Rule/CharCaseTest.php
@@ -0,0 +1,33 @@
+<?php
+namespace Aura\Filter\Rule;
+
+class CharCaseTest extends \PHPUnit_Framework_TestCase
+{
+    public function testLower()
+    {
+        $fake = new FakeCharCase();
+        $this->assertSame(
+            'abcdef',
+            $fake->strtolower('ABCDEF')
+        );
+    }
+
+    public function testUpper()
+    {
+        $fake = new FakeCharCase();
+        $this->assertSame(
+            'ABCDEF',
+            $fake->strtoupper('abcdef')
+        );
+    }
+
+    public function testUcWords()
+    {
+        $fake = new FakeCharCase();
+        $this->assertSame(
+            'Abc Def',
+            $fake->ucwords('abc def')
+        );
+    }
+
+}
diff --git a/tests/Rule/FakeCharCase.php b/tests/Rule/FakeCharCase.php
new file mode 100644
index 00000000..fe689936
--- /dev/null
+++ b/tests/Rule/FakeCharCase.php
@@ -0,0 +1,25 @@
+<?php
+namespace Aura\Filter\Rule;
+
+class FakeCharCase extends AbstractCharCase
+{
+    protected function mbstring()
+    {
+        return false;
+    }
+
+    public function strtolower($str)
+    {
+        return parent::strtolower($str);
+    }
+
+    public function strtoupper($str)
+    {
+        return parent::strtoupper($str);
+    }
+
+    public function ucwords($str)
+    {
+        return parent::ucwords($str);
+    }
+}
diff --git a/tests/Rule/Sanitize/CaseLowerTest.php b/tests/Rule/Sanitize/CaseLowerTest.php
new file mode 100644
index 00000000..81a4bd92
--- /dev/null
+++ b/tests/Rule/Sanitize/CaseLowerTest.php
@@ -0,0 +1,18 @@
+<?php
+namespace Aura\Filter\Rule\Sanitize;
+
+class CaseLowerTest extends AbstractSanitizeTest
+{
+    public function providerTo()
+    {
+        return array(
+            array(array(), false, array()),
+            array('A', true, 'a'),
+            array('AbCd', true, 'abcd'),
+            array('ABCDEF', true, 'abcdef'),
+            array('Ж', true, 'ж'),
+            array('АБВГ', true, 'абвг'),
+            array('АБВГДЕ', true, 'абвгде'),
+        );
+    }
+}
diff --git a/tests/Rule/Sanitize/CaseTitleTest.php b/tests/Rule/Sanitize/CaseTitleTest.php
new file mode 100644
index 00000000..ee874314
--- /dev/null
+++ b/tests/Rule/Sanitize/CaseTitleTest.php
@@ -0,0 +1,18 @@
+<?php
+namespace Aura\Filter\Rule\Sanitize;
+
+class CaseTitleTest extends AbstractSanitizeTest
+{
+    public function providerTo()
+    {
+        return array(
+            array(array(), false, array()),
+            array('A', true, 'A'),
+            array('Ab cd', true, 'Ab Cd'),
+            array('ABC DEF', true, 'Abc Def'),
+            array('Ж', true, 'Ж'),
+            array('АБ ВГ', true, 'Аб Вг'),
+            array('АбвГ ДЕ', true, 'Абвг Де'),
+        );
+    }
+}
diff --git a/tests/Rule/Sanitize/CaseUpperTest.php b/tests/Rule/Sanitize/CaseUpperTest.php
new file mode 100644
index 00000000..b24f24fb
--- /dev/null
+++ b/tests/Rule/Sanitize/CaseUpperTest.php
@@ -0,0 +1,18 @@
+<?php
+namespace Aura\Filter\Rule\Sanitize;
+
+class CaseUpperTest extends AbstractSanitizeTest
+{
+    public function providerTo()
+    {
+        return array(
+            array(array(), false, array()),
+            array('a', true, 'A'),
+            array('Ab cd', true, 'AB CD'),
+            array('ABC DEF', true, 'ABC DEF'),
+            array('ж', true, 'Ж'),
+            array('АБ ВГ', true, 'АБ ВГ'),
+            array('АбвГ ДЕ', true, 'АБВГ ДЕ'),
+        );
+    }
+}
diff --git a/tests/Rule/Validate/CaseLowerTest.php b/tests/Rule/Validate/CaseLowerTest.php
new file mode 100644
index 00000000..3346beba
--- /dev/null
+++ b/tests/Rule/Validate/CaseLowerTest.php
@@ -0,0 +1,26 @@
+<?php
+namespace Aura\Filter\Rule\Validate;
+
+class CaseLowerTest extends AbstractValidateTest
+{
+    public function providerIs()
+    {
+        return array(
+            array('abcd'),
+            array('efgh'),
+            array('абвв'),
+            array('фгег'),
+        );
+    }
+
+    public function providerIsNot()
+    {
+        return array(
+            array(array()),
+            array('aBcd'),
+            array('Efgh'),
+            array('АБВВ'),
+            array('ФГег'),
+        );
+    }
+}
diff --git a/tests/Rule/Validate/CaseTitleTest.php b/tests/Rule/Validate/CaseTitleTest.php
new file mode 100644
index 00000000..314bb6ae
--- /dev/null
+++ b/tests/Rule/Validate/CaseTitleTest.php
@@ -0,0 +1,28 @@
+<?php
+
+namespace Aura\Filter\Rule\Validate;
+
+class CaseTitleTest extends AbstractValidateTest
+{
+    public function providerIs()
+    {
+        return array(
+            array('Ab Cd'),
+            array('Efgh'),
+            array('Аб Вв'),
+            array('Фг Ег'),
+        );
+    }
+
+    public function providerIsNot()
+    {
+        return array(
+            array(array()),
+            array('aBcd'),
+            array('Ef gH'),
+            array('АБ ВВ'),
+            array('ФГ ег'),
+        );
+    }
+}
+
diff --git a/tests/Rule/Validate/CaseUpperTest.php b/tests/Rule/Validate/CaseUpperTest.php
new file mode 100644
index 00000000..ba66e0b8
--- /dev/null
+++ b/tests/Rule/Validate/CaseUpperTest.php
@@ -0,0 +1,28 @@
+<?php
+
+namespace Aura\Filter\Rule\Validate;
+
+class CaseUpperTest extends AbstractValidateTest
+{
+    public function providerIs()
+    {
+        return array(
+            array('AB CD'),
+            array('EFGH'),
+            array('АБ ВВ'),
+            array('ФГ ЕГ'),
+        );
+    }
+
+    public function providerIsNot()
+    {
+        return array(
+            array(array()),
+            array('aBcD'),
+            array('Ef gH'),
+            array('Аб ВВ'),
+            array('ФГ ег'),
+        );
+    }
+}
+