diff --git a/tox.ini b/tox.ini
index a13a975e..e4f8e456 100644
--- a/tox.ini
+++ b/tox.ini
@@ -13,7 +13,7 @@
 [tox]
 # "-full" variants include optional dependencies, to ensure
 # that things work both in a bare install and with all the extras.
-envlist = py27-full, py27-curl, py25-full, py32, pypy, py25, py26, py26-full, py27
+envlist = py27-full, py27-curl, py25-full, py32, pypy, py25, py26, py26-full, py27, py33
 [testenv]
 commands = python -m tornado.test.runtests {posargs:}
 
@@ -70,3 +70,7 @@ commands = python -m tornado.test.runtests --httpclient=tornado.curl_httpclient.
 # pypy, but doesn't work.
 
 # No py32-full yet: none of our dependencies currently work on python3.
+
+[testenv:py33]
+# tox doesn't yet know "py33" by default
+basepython = python3.3
\ No newline at end of file