diff --git a/src/CachingDocBlockFactory.php b/src/CachingDocBlockFactory.php
new file mode 100644
index 00000000..ee693207
--- /dev/null
+++ b/src/CachingDocBlockFactory.php
@@ -0,0 +1,72 @@
+<?php
+declare(strict_types=1);
+
+namespace LanguageServer;
+
+use Microsoft\PhpParser\Node;
+use phpDocumentor\Reflection\DocBlock;
+use phpDocumentor\Reflection\DocBlockFactory;
+use phpDocumentor\Reflection\Types;
+
+/**
+ * Caches DocBlocks by node start position and file URI.
+ */
+class CachingDocBlockFactory
+{
+    /**
+     * Maps file + node start positions to DocBlocks.
+     */
+    private $cache = [];
+
+    /**
+     * @var DocBlockFactory
+     */
+    private $docBlockFactory;
+
+
+    public function __construct()
+    {
+        $this->docBlockFactory = DocBlockFactory::createInstance();
+    }
+
+    /**
+     * @return DocBlock|null
+     */
+    public function getDocBlock(Node $node)
+    {
+        $cacheKey = $node->getStart() . ':' . $node->getUri();
+        if (array_key_exists($cacheKey, $this->cache)) {
+            return $this->cache[$cacheKey];
+        }
+        $text = $node->getDocCommentText();
+        return $this->cache[$cacheKey] = $text === null ? null : $this->createDocBlockFromNodeAndText($node, $text);
+    }
+
+    public function clearCache()
+    {
+        $this->cache = [];
+    }
+
+    /**
+     * @return DocBlock|null
+     */
+    private function createDocBlockFromNodeAndText(Node $node, string $text)
+    {
+        list($namespaceImportTable,,) = $node->getImportTablesForCurrentScope();
+        $namespaceImportTable = array_map('strval', $namespaceImportTable);
+        $namespaceDefinition = $node->getNamespaceDefinition();
+        if ($namespaceDefinition !== null && $namespaceDefinition->name !== null) {
+            $namespaceName = (string)$namespaceDefinition->name->getNamespacedName();
+        } else {
+            $namespaceName = 'global';
+        }
+        $context = new Types\Context($namespaceName, $namespaceImportTable);
+        try {
+            // create() throws when it thinks the doc comment has invalid fields.
+            // For example, a @see tag that is followed by something that doesn't look like a valid fqsen will throw.
+            return $this->docBlockFactory->create($text, $context);
+        } catch (\InvalidArgumentException $e) {
+            return null;
+        }
+    }
+}
diff --git a/src/DefinitionResolver.php b/src/DefinitionResolver.php
index 990c1965..145c6d7f 100644
--- a/src/DefinitionResolver.php
+++ b/src/DefinitionResolver.php
@@ -8,9 +8,7 @@
 use Microsoft\PhpParser;
 use Microsoft\PhpParser\Node;
 use Microsoft\PhpParser\FunctionLike;
-use phpDocumentor\Reflection\{
-    DocBlock, DocBlockFactory, Fqsen, Type, TypeResolver, Types
-};
+use phpDocumentor\Reflection\{DocBlock, Fqsen, Type, TypeResolver, Types};
 
 class DefinitionResolver
 {
@@ -29,11 +27,11 @@ class DefinitionResolver
     private $typeResolver;
 
     /**
-     * Parses Doc Block comments given the DocBlock text and import tables at a position.
+     * Parses and caches Doc Block comments given Node.
      *
-     * @var DocBlockFactory
+     * @var CachingDocBlockFactory
      */
-    private $docBlockFactory;
+    private $cachingDocBlockFactory;
 
     /**
      * Creates SignatureInformation
@@ -49,7 +47,7 @@ public function __construct(ReadableIndex $index)
     {
         $this->index = $index;
         $this->typeResolver = new TypeResolver;
-        $this->docBlockFactory = DocBlockFactory::createInstance();
+        $this->cachingDocBlockFactory = new CachingDocBlockFactory;
         $this->signatureInformationFactory = new SignatureInformationFactory($this);
     }
 
@@ -114,14 +112,14 @@ public function getDocumentationFromNode($node)
             $variableName = $node->getName();
 
             $functionLikeDeclaration = ParserHelpers\getFunctionLikeDeclarationFromParameter($node);
-            $docBlock = $this->getDocBlock($functionLikeDeclaration);
+            $docBlock = $this->cachingDocBlockFactory->getDocBlock($functionLikeDeclaration);
 
             $parameterDocBlockTag = $this->tryGetDocBlockTagForParameter($docBlock, $variableName);
             return $parameterDocBlockTag !== null ? $parameterDocBlockTag->getDescription()->render() : null;
         }
 
         // For everything else, get the doc block summary corresponding to the current node.
-        $docBlock = $this->getDocBlock($node);
+        $docBlock = $this->cachingDocBlockFactory->getDocBlock($node);
         if ($docBlock !== null) {
             // check whether we have a description, when true, add a new paragraph
             // with the description
@@ -136,40 +134,6 @@ public function getDocumentationFromNode($node)
         return null;
     }
 
-    /**
-     * Gets Doc Block with resolved names for a Node
-     *
-     * @param Node $node
-     * @return DocBlock|null
-     */
-    private function getDocBlock(Node $node)
-    {
-        // TODO make more efficient (caching, ensure import table is in right format to begin with)
-        $docCommentText = $node->getDocCommentText();
-        if ($docCommentText !== null) {
-            list($namespaceImportTable,,) = $node->getImportTablesForCurrentScope();
-            foreach ($namespaceImportTable as $alias => $name) {
-                $namespaceImportTable[$alias] = (string)$name;
-            }
-            $namespaceDefinition = $node->getNamespaceDefinition();
-            if ($namespaceDefinition !== null && $namespaceDefinition->name !== null) {
-                $namespaceName = (string)$namespaceDefinition->name->getNamespacedName();
-            } else {
-                $namespaceName = 'global';
-            }
-            $context = new Types\Context($namespaceName, $namespaceImportTable);
-
-            try {
-                // create() throws when it thinks the doc comment has invalid fields.
-                // For example, a @see tag that is followed by something that doesn't look like a valid fqsen will throw.
-                return $this->docBlockFactory->create($docCommentText, $context);
-            } catch (\InvalidArgumentException $e) {
-                return null;
-            }
-        }
-        return null;
-    }
-
     /**
      * Create a Definition for a definition node
      *
@@ -346,6 +310,11 @@ public function resolveReferenceNodeToFqn(Node $node)
         return null;
     }
 
+    public function clearCache()
+    {
+        $this->cachingDocBlockFactory->clearCache();
+    }
+
     private function resolveQualifiedNameNodeToFqn(Node\QualifiedName $node)
     {
         $parent = $node->parent;
@@ -1080,7 +1049,7 @@ public function getTypeFromNode($node)
             //  function foo($a)
             $functionLikeDeclaration = ParserHelpers\getFunctionLikeDeclarationFromParameter($node);
             $variableName = $node->getName();
-            $docBlock = $this->getDocBlock($functionLikeDeclaration);
+            $docBlock = $this->cachingDocBlockFactory->getDocBlock($functionLikeDeclaration);
 
             $parameterDocBlockTag = $this->tryGetDocBlockTagForParameter($docBlock, $variableName);
             if ($parameterDocBlockTag !== null && ($type = $parameterDocBlockTag->getType())) {
@@ -1117,7 +1086,7 @@ public function getTypeFromNode($node)
         //   3. TODO: infer from return statements
         if ($node instanceof PhpParser\FunctionLike) {
             // Functions/methods
-            $docBlock = $this->getDocBlock($node);
+            $docBlock = $this->cachingDocBlockFactory->getDocBlock($node);
             if (
                 $docBlock !== null
                 && !empty($returnTags = $docBlock->getTagsByName('return'))
@@ -1185,7 +1154,7 @@ public function getTypeFromNode($node)
             // Property, constant or variable
             // Use @var tag
             if (
-                ($docBlock = $this->getDocBlock($declarationNode))
+                ($docBlock = $this->cachingDocBlockFactory->getDocBlock($declarationNode))
                 && !empty($varTags = $docBlock->getTagsByName('var'))
                 && ($type = $varTags[0]->getType())
             ) {
@@ -1302,7 +1271,7 @@ public static function getDefinedFqn($node)
         // namespace A\B;
         // const FOO = 5;               A\B\FOO
         // class C {
-        //   const $a, $b = 4           A\B\C::$a(), A\B\C::$b
+        //   const $a, $b = 4           A\B\C::$a, A\B\C::$b
         // }
         if (($constDeclaration = ParserHelpers\tryGetConstOrClassConstDeclaration($node)) !== null) {
             if ($constDeclaration instanceof Node\Statement\ConstDeclaration) {
diff --git a/src/LanguageServer.php b/src/LanguageServer.php
index 46281f51..48b9b86e 100644
--- a/src/LanguageServer.php
+++ b/src/LanguageServer.php
@@ -141,6 +141,10 @@ public function __construct(ProtocolReader $reader, ProtocolWriter $writer)
                         $e
                     );
                 }
+
+                // When a request is processed, clear the caches of definition resolver as not to leak memory.
+                $this->definitionResolver->clearCache();
+
                 // Only send a Response for a Request
                 // Notifications do not send Responses
                 if (AdvancedJsonRpc\Request::isRequest($msg->body)) {
diff --git a/src/PhpDocument.php b/src/PhpDocument.php
index 0ac84210..d8118dc1 100644
--- a/src/PhpDocument.php
+++ b/src/PhpDocument.php
@@ -164,6 +164,8 @@ public function updateContent(string $content)
         }
 
         $this->sourceFileNode = $treeAnalyzer->getSourceFileNode();
+
+        $this->definitionResolver->clearCache();
     }
 
     /**