diff --git a/tests/rules/test_comments_indentation.py b/tests/rules/test_comments_indentation.py
index 149b6b2..8e0fe40 100644
--- a/tests/rules/test_comments_indentation.py
+++ b/tests/rules/test_comments_indentation.py
@@ -102,13 +102,13 @@ class CommentsIndentationTestCase(RuleTestCase):
                    '  a: 1\n'
                    '  # b: 2\n'
                    '# this object is useless\n'
-                   'obj2: no\n', conf)
+                   'obj2: "no"\n', conf)
         self.check('---\n'
                    'obj1:\n'
                    '  a: 1\n'
                    '# this object is useless\n'
                    '  # b: 2\n'
-                   'obj2: no\n', conf, problem=(5, 3))
+                   'obj2: "no"\n', conf, problem=(5, 3))
         self.check('---\n'
                    'obj1:\n'
                    '  a: 1\n'
diff --git a/tests/rules/test_truthy.py b/tests/rules/test_truthy.py
new file mode 100644
index 0000000..bb16a0c
--- /dev/null
+++ b/tests/rules/test_truthy.py
@@ -0,0 +1,40 @@
+# -*- coding: utf-8 -*-
+# Copyright (C) 2016 Peter Ericson
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+from tests.common import RuleTestCase
+
+
+class TruthyTestCase(RuleTestCase):
+    rule_id = 'truthy'
+
+    def test_disabled(self):
+        conf = 'truthy: disable'
+        self.check('---\n'
+                   '1: True\n', conf)
+        self.check('---\n'
+                   'True: 1\n', conf)
+
+    def test_enabled(self):
+        conf = 'truthy: enable\n'
+        self.check('---\n'
+                   '1: True\n', conf, problem=(2, 4))
+        self.check('---\n'
+                   'True: 1\n', conf, problem=(2, 1))
+        self.check('---\n'
+                   '1: "True"\n', conf)
+        self.check('---\n'
+                   '"True": 1\n', conf)
+
diff --git a/tests/test_spec_examples.py b/tests/test_spec_examples.py
index b23ad56..04d6ea7 100644
--- a/tests/test_spec_examples.py
+++ b/tests/test_spec_examples.py
@@ -119,6 +119,8 @@ conf_overrides = {
     'example-8.22': ('indentation: disable\n'),
     'example-10.1': ('colons: {max-spaces-before: 2}\n'),
     'example-10.2': ('indentation: {indent-sequences: no}\n'),
+    'example-10.8': ('truthy: disable\n'),
+    'example-10.9': ('truthy: disable\n'),
 }
 
 files = os.listdir(os.path.join(os.path.dirname(os.path.realpath(__file__)),
diff --git a/yamllint/conf/default.yaml b/yamllint/conf/default.yaml
index 9eec756..e4d720b 100644
--- a/yamllint/conf/default.yaml
+++ b/yamllint/conf/default.yaml
@@ -43,3 +43,5 @@ rules:
   new-lines:
     type: unix
   trailing-spaces: enable
+  truthy:
+    level: warning
diff --git a/yamllint/conf/relaxed.yaml b/yamllint/conf/relaxed.yaml
index f653757..fb2cdaf 100644
--- a/yamllint/conf/relaxed.yaml
+++ b/yamllint/conf/relaxed.yaml
@@ -26,3 +26,4 @@ rules:
   line-length:
     level: warning
     allow-non-breakable-inline-mappings: yes
+  truthy: disable
diff --git a/yamllint/rules/__init__.py b/yamllint/rules/__init__.py
index 6e82970..619e32d 100644
--- a/yamllint/rules/__init__.py
+++ b/yamllint/rules/__init__.py
@@ -31,6 +31,7 @@ from yamllint.rules import (
     new_line_at_end_of_file,
     new_lines,
     trailing_spaces,
+    truthy,
 )
 
 _RULES = {
@@ -50,6 +51,7 @@ _RULES = {
     new_line_at_end_of_file.ID: new_line_at_end_of_file,
     new_lines.ID: new_lines,
     trailing_spaces.ID: trailing_spaces,
+    truthy.ID: truthy,
 }
 
 
diff --git a/yamllint/rules/truthy.py b/yamllint/rules/truthy.py
new file mode 100644
index 0000000..ef0e771
--- /dev/null
+++ b/yamllint/rules/truthy.py
@@ -0,0 +1,56 @@
+# -*- coding: utf-8 -*-
+# Copyright (C) 2016 Peter Ericson
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+"""
+Use this rule to forbid truthy values that are not quoted.
+
+.. rubric:: Examples
+
+#. With ``truthy: {}``
+
+   the following code snippet would **PASS**:
+   ::
+
+    object: {"True": 1, 1: "True"}
+
+   the following code snippet would **FAIL**:
+   ::
+
+    object: {True: 1, 1: True}
+"""
+
+import yaml
+
+from yamllint.linter import LintProblem
+
+ID = 'truthy'
+TYPE = 'token'
+CONF = {}
+
+TRUTHY = ['YES', 'Yes', 'yes',
+          'NO', 'No', 'no',
+          'TRUE', 'True',  # true is a boolean
+          'FALSE', 'False',  # false is a boolean
+          'ON', 'On', 'on',
+          'OFF', 'Off', 'off']
+
+
+def check(conf, token, prev, next, nextnext, context):
+    if isinstance(token, yaml.tokens.ScalarToken):
+        if token.value in TRUTHY and token.style is None:
+            yield LintProblem(token.start_mark.line + 1,
+                              token.start_mark.column + 1,
+                              "truthy value is not quoted")