Students frequently miss tutorial classes and those who do attend often come ill-prepared, or are content to do little while waiting for the answers to be given. In problem-based engineering subjects, such as mathematics and physics, tutorial problems are assigned to build skills in the procedures taught in lectures. Lack of practice is a hindrance to student progress. This article discusses the use of continual co-assessment in tutorials in an attempt to address the problems of poor attendance and lack of preparation for, and participation in, tutorials. It discusses the successes and failures of trials that were recently implemented in an engineering course.