ISFET glucose and sucrose sensors with a platinum electrode and photopolymeric enzyme membrane have been fabricated. The platinum working electrode is used for the electrolysis of hydrogen peroxide, one of the by-products of the enzyme reaction, to improve the sensing characteristics of the sensors. To improve the response time, a photo-crosslinkable polymer (PVA-SbQ) is used in the matrix for the enzyme-immobilized membrane. The characteristics of glucose and sucrose sensors are investigated according to the variation of the platinum electrode area. The response time is about 3-5 min and determination of glucose and sucrose in the range of about 30-300 mg dl - 1 is possible.