diff --git a/python/requirements.txt b/python/requirements.txt
index 0fd2ec69b5..04dfde88c0 100644
--- a/python/requirements.txt
+++ b/python/requirements.txt
@@ -1,2 +1,6 @@
 pip==9.0.1
+setuptools==38.2.4
 wheel==0.30.0a0
+
+# For tests
+mock==2.0.0
diff --git a/python/whl.bzl b/python/whl.bzl
index 45c08d53ea..496755671f 100644
--- a/python/whl.bzl
+++ b/python/whl.bzl
@@ -44,7 +44,7 @@ whl_library = repository_rule(
         "extras": attr.string_list(),
         "_script": attr.label(
             executable = True,
-            default = Label("//rules_python:whl.py"),
+            default = Label("//tools:whltool.par"),
             cfg = "host",
         ),
     },
diff --git a/rules_python/BUILD b/rules_python/BUILD
index e0bf79667e..6c23e01ae7 100644
--- a/rules_python/BUILD
+++ b/rules_python/BUILD
@@ -16,10 +16,14 @@ package(default_visibility = ["//visibility:public"])
 licenses(["notice"])  # Apache 2.0
 
 load("//python:python.bzl", "py_binary", "py_library", "py_test")
+load("@piptool_deps//:requirements.bzl", "requirement")
 
 py_library(
     name = "whl",
     srcs = ["whl.py"],
+    deps = [
+        requirement("setuptools"),
+    ],
 )
 
 py_test(
@@ -32,18 +36,29 @@ py_test(
         "@grpc_whl//file",
         "@mock_whl//file",
     ],
-    deps = [":whl"],
+    deps = [
+        ":whl",
+        requirement("mock"),
+    ],
 )
 
 load("@subpar//:subpar.bzl", "par_binary")
-load("@piptool_deps//:requirements.bzl", "all_requirements")
 
-# TODO(mattmoor): Bundle this tool as a PAR without any
-# system-installed pre-requisites.  See TODOs in piptool.py.
 par_binary(
     name = "piptool",
     srcs = ["piptool.py"],
     deps = [
         ":whl",
-    ] + all_requirements,
+        requirement("pip"),
+        requirement("wheel"),
+    ],
+)
+
+par_binary(
+    name = "whltool",
+    srcs = ["whl.py"],
+    main = "whl.py",
+    deps = [
+        ":whl",
+    ],
 )
diff --git a/rules_python/whl.py b/rules_python/whl.py
index e3829bd9d6..c102d035c4 100644
--- a/rules_python/whl.py
+++ b/rules_python/whl.py
@@ -16,6 +16,7 @@
 import argparse
 import json
 import os
+import pkg_resources
 import re
 import zipfile
 
@@ -86,10 +87,10 @@ def dependencies(self, extra=None):
       if requirement.get('extra') != extra:
         # Match the requirements for the extra we're looking for.
         continue
-      if 'environment' in requirement:
-        # TODO(mattmoor): What's the best way to support "environment"?
-        # This typically communicates things like python version (look at
-        # "wheel" for a good example)
+      marker = requirement.get('environment')
+      if marker and not pkg_resources.evaluate_marker(marker):
+        # The current environment does not match the provided PEP 508 marker,
+        # so ignore this requirement.
         continue
       requires = requirement.get('requires', [])
       for entry in requires:
diff --git a/rules_python/whl_test.py b/rules_python/whl_test.py
index c56a4e997d..a63d625088 100644
--- a/rules_python/whl_test.py
+++ b/rules_python/whl_test.py
@@ -15,6 +15,8 @@
 import os
 import unittest
 
+from mock import patch
+
 from rules_python import whl
 
 
@@ -54,32 +56,65 @@ def test_whl_with_METADATA_file(self):
     self.assertEqual(set(wheel.dependencies()), set())
     self.assertEqual('pypi__futures_2_2_0', wheel.repository_name())
 
-  def test_mock_whl(self):
+  @patch('platform.python_version', return_value='2.7.13')
+  def test_mock_whl(self, *args):
     td = TestData('mock_whl/file/mock-2.0.0-py2.py3-none-any.whl')
     wheel = whl.Wheel(td)
     self.assertEqual(wheel.name(), 'mock')
     self.assertEqual(wheel.distribution(), 'mock')
     self.assertEqual(wheel.version(), '2.0.0')
     self.assertEqual(set(wheel.dependencies()),
-                     set(['pbr', 'six']))
+                     set(['funcsigs', 'pbr', 'six']))
     self.assertEqual('pypi__mock_2_0_0', wheel.repository_name())
+
+  @patch('platform.python_version', return_value='3.3.0')
+  def test_mock_whl_3_3(self, *args):
+    td = TestData('mock_whl/file/mock-2.0.0-py2.py3-none-any.whl')
+    wheel = whl.Wheel(td)
+    self.assertEqual(set(wheel.dependencies()),
+                     set(['pbr', 'six']))
+
+  @patch('platform.python_version', return_value='2.7.13')
+  def test_mock_whl_extras(self, *args):
+    td = TestData('mock_whl/file/mock-2.0.0-py2.py3-none-any.whl')
+    wheel = whl.Wheel(td)
     self.assertEqual(['docs', 'test'], wheel.extras())
-    self.assertEqual(set(wheel.dependencies(extra='docs')), set())
+    self.assertEqual(set(wheel.dependencies(extra='docs')), set(['sphinx']))
     self.assertEqual(set(wheel.dependencies(extra='test')), set(['unittest2']))
 
-  def test_google_cloud_language_whl(self):
+  @patch('platform.python_version', return_value='3.0.0')
+  def test_mock_whl_extras_3_0(self, *args):
+    td = TestData('mock_whl/file/mock-2.0.0-py2.py3-none-any.whl')
+    wheel = whl.Wheel(td)
+    self.assertEqual(['docs', 'test'], wheel.extras())
+    self.assertEqual(set(wheel.dependencies(extra='docs')), set(['sphinx', 'Pygments', 'jinja2']))
+    self.assertEqual(set(wheel.dependencies(extra='test')), set(['unittest2']))
+
+  @patch('platform.python_version', return_value='2.7.13')
+  def test_google_cloud_language_whl(self, *args):
     td = TestData('google_cloud_language_whl/file/' +
                   'google_cloud_language-0.29.0-py2.py3-none-any.whl')
     wheel = whl.Wheel(td)
     self.assertEqual(wheel.name(), 'google-cloud-language')
     self.assertEqual(wheel.distribution(), 'google_cloud_language')
     self.assertEqual(wheel.version(), '0.29.0')
+    expected_deps = ['google-gax', 'google-cloud-core',
+                     'googleapis-common-protos[grpc]', 'enum34']
     self.assertEqual(set(wheel.dependencies()),
-                     set(['google-gax', 'google-cloud-core',
-                          'googleapis-common-protos[grpc]']))
+                     set(expected_deps))
     self.assertEqual('pypi__google_cloud_language_0_29_0',
                      wheel.repository_name())
     self.assertEqual([], wheel.extras())
 
+  @patch('platform.python_version', return_value='3.4.0')
+  def test_google_cloud_language_whl_3_4(self, *args):
+    td = TestData('google_cloud_language_whl/file/' +
+                  'google_cloud_language-0.29.0-py2.py3-none-any.whl')
+    wheel = whl.Wheel(td)
+    expected_deps = ['google-gax', 'google-cloud-core',
+                     'googleapis-common-protos[grpc]']
+    self.assertEqual(set(wheel.dependencies()),
+                     set(expected_deps))
+
 if __name__ == '__main__':
   unittest.main()
diff --git a/tools/BUILD b/tools/BUILD
index 117d343233..a2e3977403 100644
--- a/tools/BUILD
+++ b/tools/BUILD
@@ -16,4 +16,4 @@ package(default_visibility = ["//visibility:public"])
 licenses(["notice"])  # Apache 2.0
 
 # This is generated and updated by ./update_tools.sh
-exports_files(["piptool.par"])
+exports_files(["piptool.par", "whltool.par"])
diff --git a/tools/piptool.par b/tools/piptool.par
index 41019234d3..ee03cfc320 100755
Binary files a/tools/piptool.par and b/tools/piptool.par differ
diff --git a/tools/whltool.par b/tools/whltool.par
new file mode 100755
index 0000000000..6c06a50e25
Binary files /dev/null and b/tools/whltool.par differ
diff --git a/update_tools.sh b/update_tools.sh
index 7eb84500a2..5f00e9c331 100755
--- a/update_tools.sh
+++ b/update_tools.sh
@@ -16,5 +16,6 @@
 
 set -euo pipefail
 
-bazel build //rules_python:piptool.par
+bazel build //rules_python:piptool.par //rules_python:whltool.par
 cp bazel-bin/rules_python/piptool.par tools/piptool.par
+cp bazel-bin/rules_python/whltool.par tools/whltool.par