diff --git a/tox.ini b/tox.ini
index 4bf2d16c..b3f0a3f6 100644
--- a/tox.ini
+++ b/tox.ini
@@ -33,6 +33,7 @@ envlist =
 
         # Alternate Resolvers.
         py2-caresresolver, py3-caresresolver,
+        py2-threadedresolver, py3-threadedresolver,
 
         # Other configurations; see comments below.
         py2-monotonic, py3-monotonic,
@@ -225,6 +226,16 @@ basepython = python3.2
 deps = {[testenv:py32-full]deps}
 commands = python -m tornado.test.runtests --resolver=tornado.platform.caresresolver.CaresResolver {posargs:}
 
+[testenv:py2-threadedresolver]
+basepython = python2.7
+deps = {[testenv:py27-full]deps}
+commands = python -m tornado.test.runtests --resolver=tornado.netutil.ThreadedResolver {posargs:}
+
+[testenv:py3-threadedresolver]
+basepython = python3.4
+deps = {[testenv:py34-full]deps}
+commands = python -m tornado.test.runtests --resolver=tornado.netutil.ThreadedResolver {posargs:}
+
 [testenv:py2-monotonic]
 basepython = python2.7
 deps =