diff --git a/doc/core/man/trial.1 b/doc/core/man/trial.1
index f01934d..1b89412 100644
--- a/doc/core/man/trial.1
+++ b/doc/core/man/trial.1
@@ -13,7 +13,8 @@ packages and files listed on the command line.
 trial will take either filenames or fully qualified Python names as
 arguments.  Thus `trial myproject/foo.py', `trial myproject.foo' and
 `trial myproject.foo.SomeTestCase.test_method' are all valid ways to
-invoke trial.
+invoke trial. Multiple such arguments are also accepted, and their order will
+determine the order in which the corresponding tests are run.
 .PP
 After running the given test suite, the default test reporter prints a summary
 of the test run. This consists of the word "PASSED" (if all tests ran as
diff --git a/twisted/scripts/trial.py b/twisted/scripts/trial.py
index 349b0c6..e57a22f 100644
--- a/twisted/scripts/trial.py
+++ b/twisted/scripts/trial.py
@@ -4,7 +4,7 @@
 # See LICENSE for details.
 
 
-import sys, os, random, gc, time, warnings
+import sys, os, collections, random, gc, time, warnings
 
 from twisted.internet import defer
 from twisted.application import app
@@ -93,6 +93,35 @@ def _reporterAction():
     return usage.CompleteList([p.longOpt for p in
                                plugin.getPlugins(itrial.IReporter)])
 
+
+class _OrderedSet(collections.MutableSet):
+    def __init__(self, contents=()):
+        self._contents = collections.OrderedDict()
+        self.update(contents)
+
+    def __contains__(self, e):
+        return e in self._contents
+
+    def __iter__(self):
+        return iter(self._contents)
+
+    def __len__(self):
+        return len(self._contents)
+
+    def __repr__(self):
+        return "%s(%s)" % (self.__class__.__name__, list(self._contents))
+
+    def add(self, e):
+        self._contents[e] = None
+
+    def discard(self, e):
+        if e in self._contents:
+            del self._contents[e]
+
+    def update(self, contents):
+        self._contents.update((e, None) for e in contents)
+
+
 class Options(usage.Options, app.ReactorSelectionMixin):
     synopsis = """%s [options] [[file|package|module|TestCase|testmethod]...]
     """ % (os.path.basename(sys.argv[0]),)
@@ -146,7 +175,7 @@ class Options(usage.Options, app.ReactorSelectionMixin):
     tracer = None
 
     def __init__(self):
-        self['tests'] = set()
+        self['tests'] = _OrderedSet()
         usage.Options.__init__(self)
 
 
diff --git a/twisted/trial/test/test_script.py b/twisted/trial/test/test_script.py
index 6c93ebe..bcae843 100644
--- a/twisted/trial/test/test_script.py
+++ b/twisted/trial/test/test_script.py
@@ -480,3 +480,26 @@ class ExtraTests(unittest.TestCase):
         self.assertDeprecationWarning(self.config.opt_extra,
                                       self.flushWarnings([self.test_xDeprecation]))
 
+
+
+class TestArgumentOrderTests(unittest.TestCase):
+    def setUp(self):
+        self.config = trial.Options()
+        self.loader = runner.TestLoader()
+
+    def test_preserveArgumentOrder(self):
+        """
+        Multiple tests passed on the command line should not be reordered.
+
+        """
+
+        tests = ["foo", "bar", "quux", "baz"]
+        self.config.parseOptions(tests)
+
+        suite = trial._getSuite(self.config)
+        names = testNames(suite)
+
+        expected_suite = runner.TestSuite(map(self.loader.loadByName, tests))
+        expected_names = testNames(expected_suite)
+
+        self.assertEqual(names, expected_names)