Grease a 9" square pan.
In a large sauce pan melt butter over medium heat. Add marshmallows and melt, stirring constantly to prevent scorching.
Remove from heat and stir in cereal until well coated.
Press marshmallow coated cereal into the prepared pan. Sprinkle chocolate chips across the top. Place pan in refrigerator immediately to prevent chips from melting.
Cut into bars when firm.