BACKGROUND Computer-based instruction has been introduced at the University of North Carolina at Chapel Hill to augment its nutrition course for first-year medical students. Seven program modules have been completed; 2 more are planned. Each module explains the biochemistry and physiology of nutrition through interactive lessons, exercises, and a video case study. OBJECTIVE The goal of this study was to evaluate the instructional efficacy and acceptability of the nutrition and cancer module when used by first-year medical students. DESIGN The module was used by 163 first-year medical students at the university's medical school as an obligatory component of the nutrition course. Before and after using the module, students were asked to answer multiple-choice questions concerning their knowledge and attitudes; each question had 5 possible answers. RESULTS On average, students spent approximately 3 h studying the lessons. The percentage of correct responses to 20 knowledge questions increased from 22% before the module was used to 86% immediately after its use. When a randomly selected subsample of 25% of the students took the same test 3 mo later, they answered 62% of the questions correctly. The increase in the percentage of students who felt prepared to provide advice regarding nutrition's role in cancer prevention (from 5.7% to 66.9%) suggested a successful subjective learning experience. Neither the students' initial level of interest in cancer nutrition nor their acceptance of computer-based instruction was related to learning outcome. CONCLUSIONS The tested module is a useful and effective aid for teaching nutritional principles of cancer prevention. The evaluation strategy helped identify areas for instructional improvement.