diff --git a/lib/process_shared.rb b/lib/process_shared.rb
index 2ef9257..03348c8 100644
--- a/lib/process_shared.rb
+++ b/lib/process_shared.rb
@@ -29,4 +29,5 @@ require 'process_shared/binary_semaphore'
 require 'process_shared/mutex'
 require 'process_shared/condition_variable'
 require 'process_shared/monitor'
+require 'process_shared/monitor_mixin'
 
diff --git a/lib/process_shared/monitor_mixin.rb b/lib/process_shared/monitor_mixin.rb
new file mode 100644
index 0000000..de2d06a
--- /dev/null
+++ b/lib/process_shared/monitor_mixin.rb
@@ -0,0 +1,42 @@
+require 'process_shared'
+
+module ProcessShared
+  module MonitorMixin
+    def self.extended(obj)
+      obj.send :mon_initialize
+    end
+
+    def mon_enter
+      @mon_monitor.lock
+    end
+    
+    def mon_exit
+      @mon_monitor.unlock
+    end
+    
+    def mon_synchronize
+      mon_enter
+      begin
+        yield
+      ensure
+        mon_exit
+      end
+    end
+    alias_method :synchronize, :mon_synchronize
+    
+    def mon_try_enter
+      raise NotImplementedError, 'not implemented'
+    end
+    alias_method :try_mon_enter, :mon_try_enter
+    
+    def new_cond
+      raise NotImplementedError, 'not implemented'
+    end
+
+    private
+
+    def mon_initialize
+      @mon_monitor = Monitor.new
+    end
+  end
+end
diff --git a/spec/process_shared/monitor_mixin_spec.rb b/spec/process_shared/monitor_mixin_spec.rb
new file mode 100644
index 0000000..62e0483
--- /dev/null
+++ b/spec/process_shared/monitor_mixin_spec.rb
@@ -0,0 +1,33 @@
+require 'spec_helper'
+require 'process_shared'
+
+module ProcessShared
+  describe MonitorMixin do
+
+    before :each do
+      @obj = Object.new
+      @obj.extend(MonitorMixin)
+    end
+
+    it 'raises exception when unlocked by other process' do
+      pid = Kernel.fork do
+        @obj.mon_enter
+        sleep 0.2
+        @obj.mon_exit
+        Kernel.exit!
+      end
+
+      sleep 0.1
+      proc { @obj.mon_exit }.must_raise(ProcessError)
+
+      ::Process.wait(pid)
+    end
+
+    it 'raises nothing with nested lock' do
+      @obj.mon_enter
+      @obj.mon_enter
+      @obj.mon_exit
+      @obj.mon_exit
+    end
+  end
+end