diff --git a/.travis.yml b/.travis.yml
index f359de1be..d9a0f57d5 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -3,81 +3,56 @@ language: python
 os:
   - linux
 
-python:
-  - "pypy"
-  - "2.6"
-  - "2.7"
-  - "3.2"
-  - "3.3"
-  - "3.4"
+env:
+  matrix:
+    # Supported environments:
+    - TOX_ENV=pypy
+    - TOX_ENV=py26
+    - TOX_ENV=py27
+    - TOX_ENV=py32
+    - TOX_ENV=py33
+
+    # Also run the tests against cryptography master.
+    - TOX_ENV=pypy-cryptographymaster
+    - TOX_ENV=py26-cryptographymaster
+    - TOX_ENV=py27-cryptographymaster
+    - TOX_ENV=py32-cryptographymaster
+    - TOX_ENV=py33-cryptographymaster
+
+    # Also run at least a little bit against an older version of OpenSSL.
+    - TOX_ENV=py27 OPENSSL=0.9.8
 
 matrix:
-  include:
-  # Also run the tests against cryptography master.
-  - python: "2.6"
-    env:
-      CRYPTOGRAPHY_GIT_MASTER=true
-  - python: "2.7"
-    env:
-      CRYPTOGRAPHY_GIT_MASTER=true
-  - python: "3.2"
-    env:
-      CRYPTOGRAPHY_GIT_MASTER=true
-  - python: "3.3"
-    env:
-      CRYPTOGRAPHY_GIT_MASTER=true
-  - python: "3.4"
-    env:
-      CRYPTOGRAPHY_GIT_MASTER=true
-  - python: "pypy"
-    env:
-      CRYPTOGRAPHY_GIT_MASTER=true
-
-  # Also run at least a little bit against an older version of OpenSSL.
-  - python: "2.7"
-    env:
-      OPENSSL=0.9.8
-
-  # Let the cryptography master builds fail because they might be triggered by
-  # cryptography changes beyond our control.
   allow_failures:
-  - env:
-      CRYPTOGRAPHY_GIT_MASTER=true
-  - env:
-      OPENSSL=0.9.8
+    # Let the cryptography master builds fail, because they might be
+    # triggered by cryptography changes beyond our control.
+    - env: TOX_ENV=pypy-cryptographymaster
+    - env: TOX_ENV=py26-cryptographymaster
+    - env: TOX_ENV=py27-cryptographymaster
+    - env: TOX_ENV=py32-cryptographymaster
+    - env: TOX_ENV=py33-cryptographymaster
 
-before_install:
-  - if [ -n "$CRYPTOGRAPHY_GIT_MASTER" ]; then pip install git+https://github.com/pyca/cryptography.git;fi
+    - env: TOX_ENV=py27 OPENSSL=0.9.8
 
 install:
-  # Install the wheel library explicitly here.  It is not really a setup
-  # dependency.  It is not an install dependency.  It is only a dependency for
-  # the script directive below - because we want to exercise wheel building on
-  # travis.
-  - pip install wheel
-
-  # Also install some tools for measuring code coverage and sending the results
-  # to coveralls.
-  - pip install coveralls coverage
-
-script:
+  # In some builds, install an old version of OpenSSL.
   - |
     if [[ "${OPENSSL}" == "0.9.8" ]]; then
       sudo add-apt-repository "deb http://archive.ubuntu.com/ubuntu/ lucid main"
       sudo apt-get -y update
       sudo apt-get install -y --force-yes libssl-dev/lucid
     fi
-  - |
-    pip install -e .
-  - |
-    coverage run --branch --source=OpenSSL setup.py bdist_wheel test
-  - |
-    coverage report -m
-  - |
-    python -c "import OpenSSL.SSL; print(OpenSSL.SSL.SSLeay_version(OpenSSL.SSL.SSLEAY_VERSION))"
+
+  # Tox actually builds our individual testing virtualenvs.
+  - pip install tox
+
+  - pip install coveralls
+
+script:
+  - tox -e $TOX_ENV
 
 after_success:
-    - coveralls
+  - coveralls
 
 notifications:
   email: false
diff --git a/tox.ini b/tox.ini
index 67386d1a8..965cb8a39 100644
--- a/tox.ini
+++ b/tox.ini
@@ -2,9 +2,77 @@
 envlist = pypy,py26,py27,py32,py33
 
 [testenv]
+deps =
+     # Only required to build wheels as part of test cycle:
+     wheel==0.23.0
+     coverage==3.7.1
 setenv =
     # Do not allowed the executing environment to pollute the test environment
     # with extra packages.
     PYTHONPATH=
-# The standard library unittest module can run tests on Python 2.7 and newer
-commands = python setup.py test
+commands =
+    # The standard library unittest module can run tests on Python 2.7 and newer
+    coverage run --branch --source=OpenSSL setup.py test
+    coverage report --show-missing
+    python setup.py bdist_wheel
+    python -c "import OpenSSL.SSL; print(OpenSSL.SSL.SSLeay_version(OpenSSL.SSL.SSLEAY_VERSION))"
+
+[testenv:pypy]
+basepython = pypy
+deps =
+    {[testenv]deps}
+    cryptography==0.4
+
+[testenv:py26]
+basepython = python2.6
+deps =
+    {[testenv]deps}
+    cryptography==0.4
+
+[testenv:py27]
+basepython = python2.7
+deps =
+    {[testenv]deps}
+    cryptography==0.4
+
+[testenv:py32]
+basepython = python3.2
+deps =
+    {[testenv]deps}
+    cryptography==0.4
+
+[testenv:py33]
+basepython = python3.3
+deps =
+    {[testenv]deps}
+    cryptography==0.4
+
+[testenv:pypy-cryptographymaster]
+basepython = pypy
+deps =
+    {[testenv]deps}
+    -egit+https://github.com/pyca/cryptography.git#egg=cryptography
+
+[testenv:py26-cryptographymaster]
+basepython = python2.6
+deps =
+    {[testenv]deps}
+    -egit+https://github.com/pyca/cryptography.git#egg=cryptography
+
+[testenv:py27-cryptographymaster]
+basepython = python2.7
+deps =
+    {[testenv]deps}
+    -egit+https://github.com/pyca/cryptography.git#egg=cryptography
+
+[testenv:py32-cryptographymaster]
+basepython = python3.2
+deps =
+    {[testenv]deps}
+    -egit+https://github.com/pyca/cryptography.git#egg=cryptography
+
+[testenv:py33-cryptographymaster]
+basepython = python3.3
+deps =
+    {[testenv]deps}
+    -egit+https://github.com/pyca/cryptography.git#egg=cryptography