Assessment in many engineering courses is mostly summative in nature. We have introduced an electronic Classroom Communication System (CCS) into undei^adiiate en^neering courses to provide students with formative assessment on a regular basis. Kxpcriences with the system are presented, including both student and instructor evaluations. Students like it because it is anonymous and lets them know in a timely manner when they have difficulty understanding new concepts. The system also helps iiifonn the instnictor about student comprehension of various concepts, well in advance of an examination, resulting in better retention of ftmdamental eoncepts. The system can help an instnictor adjust the pace of the course to match the aptitude of the students. Therefore, instnictors might reduce the variance in students" conceptual understanding of fi.indamental concepts early in the course, allowing for more uniform coverage of advanced topics later in the course.