diff --git a/flake8/engine.py b/flake8/engine.py
index 5adefae..f3314e5 100644
--- a/flake8/engine.py
+++ b/flake8/engine.py
@@ -55,8 +55,9 @@ def get_parser():
         except NotImplementedError:
             auto = 1
         parser.config_options.append('jobs')
-        parser.add_option('-j', '--jobs', type='int', default=auto,
-                          help="number of jobs to run simultaneously")
+        parser.add_option('-j', '--jobs', type='string', default='',
+                          help="number of jobs to run simultaneously, "
+                          "or 'auto'")
 
     parser.add_option('--exit-zero', action='store_true',
                       help="exit with code 0 even if there are errors")
@@ -91,11 +92,20 @@ def get_style_guide(**kwargs):
     for options_hook in options_hooks:
         options_hook(options)
 
-    if multiprocessing and options.jobs > 1:
-        reporter = BaseQReport if options.quiet else QueueReport
-        report = styleguide.init_report(reporter)
-        report.input_file = styleguide.input_file
-        styleguide.runner = report.task_queue.put
+    if multiprocessing and options.jobs:
+        if options.jobs.isdigit():
+            n_jobs = int(options.jobs)
+        else:
+            try:
+                n_jobs = multiprocessing.cpu_count()
+            except NotImplementedError:
+                n_jobs = 1
+        if n_jobs > 1:
+            options.jobs = n_jobs
+            reporter = BaseQReport if options.quiet else QueueReport
+            report = styleguide.init_report(reporter)
+            report.input_file = styleguide.input_file
+            styleguide.runner = report.task_queue.put
 
     return styleguide
 
diff --git a/flake8/tests/test_engine.py b/flake8/tests/test_engine.py
index 1032bd1..5f9d27b 100644
--- a/flake8/tests/test_engine.py
+++ b/flake8/tests/test_engine.py
@@ -34,7 +34,7 @@ class TestEngine(unittest.TestCase):
         m = mock.Mock()
         with mock.patch('flake8.engine.StyleGuide') as StyleGuide:
             with mock.patch('flake8.engine.get_parser') as get_parser:
-                StyleGuide.return_value.options.jobs = 42
+                StyleGuide.return_value.options.jobs = '42'
                 get_parser.return_value = (m, [])
                 engine.get_style_guide(foo='bar')
                 get_parser.assert_called_once_with()