diff --git a/rest_framework/serializers.py b/rest_framework/serializers.py
index da0af467f..0bacacda7 100644
--- a/rest_framework/serializers.py
+++ b/rest_framework/serializers.py
@@ -452,6 +452,9 @@ class ModelSerializer(Serializer):
         if model_field.null or model_field.blank:
             kwargs['required'] = False
 
+        if not model_field.editable:
+            kwargs['read_only'] = True
+
         if model_field.has_default():
             kwargs['required'] = False
             kwargs['default'] = model_field.get_default()
diff --git a/rest_framework/tests/fields.py b/rest_framework/tests/fields.py
new file mode 100644
index 000000000..b1a8161a6
--- /dev/null
+++ b/rest_framework/tests/fields.py
@@ -0,0 +1,26 @@
+"""
+General tests for relational fields.
+"""
+
+from django.db import models
+from django.test import TestCase
+from rest_framework import serializers
+
+
+class TimestampedModel(models.Model):
+    added = models.DateTimeField(auto_now_add=True)
+    updated = models.DateTimeField(auto_now=True)
+
+
+class TimestampedModelSerializer(serializers.ModelSerializer):
+    class Meta:
+        model = TimestampedModel
+
+
+class ReadOnlyFieldTests(TestCase):
+    def test_auto_now_fields_read_only(self):
+        """
+        auto_now and auto_now_add fields should be readonly by default.
+        """
+        serializer = TimestampedModelSerializer()
+        self.assertEquals(serializer.fields['added'].read_only, True)