Although Fred Keller's personalized system of instruction (PSI) has had a surprisingly rapid adoption in colleges and universities since its introduction in 1964, sound evaluation techniques for the method are still needed. Verbal reports are vague, while other methods that have been used are idiosyncratic and depend on the way the teacher presents the course. Oral interviews and self-pacing studies have other flaws. Much of the research to date has been sloppy, and many procedures have been introduced with only the flimsiest bit of empirical justification. Since a primary aim of PSI is to stimulate interest in the course, some dependent variables with measure interest might be studied. These might include the number and pattern of withdrawals in the course, a question-asking profile, or use of an interest library consisting of articles related to lectures which are stocked in student dormitories. Also, a self-management project might supplant traditional rat experiments in psychology courses. (JK)