In a bowl, combine cracker crumbs and butter, mix well.
Stir in sugar and peanut butter.
Press into a greased 9 inch square pan.
In a microwave or double boiler, melt the chocolate chips and stir until smooth.
Spread over peanut butter layer.
Chill for 30 minutes. Cut into squares.
Chill until firm, about 30 minutes longer.
Store airtight in refrigerator.