diff --git a/HISTORY.md b/HISTORY.md
index fe04fe2..94ed6d5 100644
--- a/HISTORY.md
+++ b/HISTORY.md
@@ -32,6 +32,9 @@ Castile 0.5
 *   Established an abstract base class for compiler backends.
 *   Fixed a bug where tagged values were being tagged again
     during a cast from a union type to another union type.
+*   ArgumentParser is used instead of OptionParser to parse
+    command-line arguments. `--version` added, `--test` (and
+    remaining doctests in source modules) removed.
 
 Castile 0.4
 -----------
diff --git a/TODO.md b/TODO.md
index c7e6ef7..d74f0d7 100644
--- a/TODO.md
+++ b/TODO.md
@@ -30,8 +30,6 @@ Test framework: collect the backend-independent tests into a single
 file, and only test it once.  Run all the *other* tests on every
 backend.
 
-Also make sure that doctests are run by test script.
-
 ### Design ###
 
 Don't output final value.  Command-line arguments passed to `main`.  (`sysmain`?)
diff --git a/src/castile/context.py b/src/castile/context.py
index 180a157..c51a685 100644
--- a/src/castile/context.py
+++ b/src/castile/context.py
@@ -3,19 +3,6 @@ class CastileContextError(ValueError):
 
 
 class ScopedContext(object):
-    """
-    >>> d = ScopedContext({ 'a': 2, 'b': 3 })
-    >>> e = ScopedContext({ 'c': 4 }, parent=d)
-    >>> e['c']
-    4
-    >>> e['b']
-    3
-    >>> 'a' in e
-    True
-    >>> 'e' in e
-    False
-
-    """
     def __init__(self, dict, parent=None, level=None):
         self._dict = dict
         self.parent = parent
@@ -47,14 +34,3 @@ def __contains__(self, key):
 
     def __repr__(self):
         return 'ScopedContext(%r,parent=%r)' % (self._dict, self.parent)
-
-
-if __name__ == "__main__":
-    import sys
-    import doctest
-    (fails, something) = doctest.testmod()
-    if fails == 0:
-        print("All tests passed.")
-        sys.exit(0)
-    else:
-        sys.exit(1)
diff --git a/src/castile/main.py b/src/castile/main.py
index 849c760..a38711c 100644
--- a/src/castile/main.py
+++ b/src/castile/main.py
@@ -6,7 +6,7 @@
 
 import sys
 
-from optparse import OptionParser
+from argparse import ArgumentParser
 
 from castile.parser import Parser
 from castile.eval import Program
@@ -16,35 +16,35 @@
 
 
 def main(argv):
-    optparser = OptionParser(__doc__.strip())
-    optparser.add_option("-a", "--show-ast",
-                         action="store_true", dest="show_ast", default=False,
-                         help="show parsed AST instead of evaluating")
-    optparser.add_option("-c", "--compile-to", metavar='BACKEND',
-                         dest="compile_to", default=None,
-                         help="compile to given backend code instead "
-                              "of evaluating directly (available backends: "
-                              "c, javascript, ruby, stackmac)")
-    optparser.add_option("-p", "--parse-only",
-                         action="store_true", dest="parse_only",
-                         default=False,
-                         help="parse the input program only and exit")
-    optparser.add_option("-t", "--test",
-                         action="store_true", dest="test", default=False,
-                         help="run test cases and exit")
-    optparser.add_option("-Y", "--no-typecheck",
-                         action="store_false", dest="typecheck", default=True,
-                         help="do not typecheck the program")
-    (options, args) = optparser.parse_args(argv[1:])
-    if options.test:
-        import doctest
-        (fails, something) = doctest.testmod()
-        if fails == 0:
-            print("All tests passed.")
-            sys.exit(0)
-        else:
-            sys.exit(1)
-    with open(args[0], 'r') as f:
+    argparser = ArgumentParser()
+
+    argparser.add_argument('input_files', nargs='+', metavar='FILENAME', type=str,
+        help='Source files containing the Castile program'
+    )
+    argparser.add_argument("-a", "--show-ast",
+        action="store_true", dest="show_ast", default=False,
+        help="show parsed AST instead of evaluating"
+    )
+    argparser.add_argument("-c", "--compile-to", metavar='BACKEND',
+        dest="compile_to", default=None,
+        help="compile to given backend code instead "
+             "of evaluating directly (available backends: "
+             "c, javascript, ruby, stackmac)"
+    )
+    argparser.add_argument("-p", "--parse-only",
+        action="store_true", dest="parse_only",
+        default=False,
+        help="parse the input program only and exit"
+    )
+    argparser.add_argument("-Y", "--no-typecheck",
+        action="store_false", dest="typecheck", default=True,
+        help="do not typecheck the program"
+    )
+    argparser.add_argument('--version', action='version', version="%(prog)s 0.5")
+
+    options = argparser.parse_args(argv[1:])
+
+    with open(options.input_files[0], 'r') as f:
         p = Parser(f.read())
         ast = p.program()
         if options.show_ast: