Measuring the clinical application of knowledge and skills acquired in specific medical school courses is a critical part of curriculum evaluation. Second-year Cancer Prevention Course (CPC) students and a comparison group were surveyed by questionnaires, cognitively tested, and a subsample participated in in-depth interviews. The 6-month and 18-month follow-up interviews indicated that more CPC students practiced prevention in their clinical rotations than did the comparison group. Direct, one-on-one access to patients during clinical training was an important mediating factor in the practice of prevention skills. In addition, a behavioral intent inventory showed that CPC students, in their future careers, intend to perform certain specific cancer prevention activities more than others. Long-term retained knowledge (75% correct) stabilized at levels significantly higher (p less than .001) than baseline test scores prior to the Cancer Prevention Course. At the time of the two follow-up exams of cognitive knowledge, the comparison group of students was able to do no better than had the CPC students at baseline before the course. Positive beliefs about cancer prevention improved over the study period. More than twice as many cancer course students attended subsequent optional lectures and reported optional reading on cancer prevention topics than did the comparison group. Overall, the study showed a lasting effect of the elective course in cancer prevention, in terms of tested knowledge, and self-reported measures of attitudes, beliefs, practice of prevention in clinical rotations, and intent to apply prevention in future practice.