PROJECTTUTOR is an intelligent tutoring system that enhances conventional classroom instruction by teaching problem solving in project planning. The domain knowledge covered by the expert module is divided into three functions. Structural analysis, identifies the activities that make up the project, time analysis, computes the earliest and latest start and finish times of each activity, as well slack times and critical paths, and cost analysis computes the minimum project time and the project costs by crashing all the activities. PROJECTTUTOR consists of two subsystems: the authoring component and the tutoring component. The authoring component, which offers natural language text and graphical network representations, is used by the teacher to specify case problems; a case problem consists of a text describing the problem and a framework describing the structure of the problem. The student uses the tutoring component to work on the case exercise. At any time, the student can ask the system to diagnose work, give hints for further solution steps, check whether a solution is correct, explain errors, or produce a (sub-)solution. A qualitative evaluation was carried out, showing that the students appreciated the advantages of the system compared to paper-and-pencil exercises. (Contains 11 references.) (AEF)