diff --git a/lib/mongo/db.rb b/lib/mongo/db.rb
index f5613f5..0e4dd2d 100644
--- a/lib/mongo/db.rb
+++ b/lib/mongo/db.rb
@@ -175,10 +175,11 @@ module Mongo
     # @param [String] password
     #
     # @return [Hash] an object representing the user.
-    def add_user(username, password)
+    def add_user(username, password, read_only = false)
       users = self[SYSTEM_USER_COLLECTION]
       user  = users.find_one({:user => username}) || {:user => username}
       user['pwd'] = Mongo::Support.hash_password(username, password)
+      user['readOnly'] = true if read_only;
       users.save(user)
       return user
     end
diff --git a/test/auxillary/authentication_test.rb b/test/auxillary/authentication_test.rb
index 83d33b4..a744d1e 100644
--- a/test/auxillary/authentication_test.rb
+++ b/test/auxillary/authentication_test.rb
@@ -26,6 +26,7 @@ class AuthenticationTest < Test::Unit::TestCase
     @admin.authenticate('bob', 'secret')
     @db1.add_user('user1', 'secret')
     @db2.add_user('user2', 'secret')
+    @db2.add_user('userRO', 'secret', true) # read-only
     @admin.logout
 
     assert_raise Mongo::OperationFailure do
@@ -53,6 +54,7 @@ class AuthenticationTest < Test::Unit::TestCase
 
     assert @db1['stuff'].insert({:a => 2}, :safe => true)
     assert @db2['stuff'].insert({:a => 2}, :safe => true)
+    assert @db2['stuff'].find(:safe => true)
 
     @db1.logout
     assert_raise Mongo::OperationFailure do
@@ -63,6 +65,12 @@ class AuthenticationTest < Test::Unit::TestCase
     assert_raise Mongo::OperationFailure do
       assert @db2['stuff'].insert({:a => 2}, :safe => true)
     end
+
+    @db2.authenticate('userRO', 'secret')
+    assert @db2['stuff'].find(:safe => true)
+    assert_raise Mongo::OperationFailure do
+      assert @db2['stuff'].insert({:a => 2}, :safe => true)
+    end
   end
 
 end
diff --git a/test/db_test.rb b/test/db_test.rb
index 910d2c8..c14dd39 100644
--- a/test/db_test.rb
+++ b/test/db_test.rb
@@ -151,6 +151,13 @@ class DBTest < Test::Unit::TestCase
     @@db.remove_user('foo:bar')
   end
 
+  def test_authenticate_read_only
+    @@db.add_user('joebob', 'user', true) # read-only user
+    assert @@db.authenticate('joebob', 'user')
+    @@db.logout
+    @@db.remove_user('joebob')
+  end
+
   def test_authenticate_with_connection_uri
     @@db.add_user('spongebob', 'squarepants')
     assert Mongo::Connection.from_uri("mongodb://spongebob:squarepants@#{host_port}/#{@@db.name}")