diff --git a/run_tests.py b/run_tests.py
index cfa92bb..8dcf69e 100644
--- a/run_tests.py
+++ b/run_tests.py
@@ -1,11 +1,24 @@
 import sys, doctest, os, glob
+from getopt import gnu_getopt as getopt
 
 CUR_DIR = os.path.dirname(os.path.abspath(__file__))
 sys.path.insert(0, CUR_DIR)
 
 if __name__ == '__main__':
+    run_level = None
+    optlist, args = getopt(sys.argv[1:], "l:", ['--level='])
+    
+    for opt, arg in optlist:
+        if opt in ("-l", "--list"):
+            run_level = arg.zfill(2)
+    
     # Test each package
-    test_files = glob.glob('%s/*.txt' % os.path.join(CUR_DIR, 'tests'))
+    if run_level is None:
+        test_files = glob.glob('%s/*.txt' % os.path.join(CUR_DIR, 'tests'))        
+    else: 
+        test_files = glob.glob('%s/%s-*.txt' % \
+            (os.path.join(CUR_DIR, 'tests'), run_level))
+    
     test_files = map(lambda i: i[len(CUR_DIR)+1:], test_files)
 
     # Run the tests