Health promotion and disease prevention must be addressed in medical education, and the assessment of future physicians' health preventive perceptions and behaviors is a critical step in the process. We conducted a cross-sectional survey of 512 medical students enrolled during the 1992-1993 academic year. Outcome measures were self-reported health behaviors and ratings of the importance of prevention. Overall, results indicated that the preponderance of respondents are engaging in healthy behaviors; however, some high-risk behaviors, such as drinking and driving and possible binge drinking, were reported by at least 15% of the respondents. Significant differences were detected regarding students' perceptions; a linear decreasing trend was noted with first-year students rating the importance of prevention the highest and fourth-year students rating it the lowest. Additionally, this study attempted to correlate health behaviors with perceptions. The results show significant relationships between student-reported behaviors and corresponding perceptions. Even though this cohort is healthy overall, some students are engaging in behaviors that are not conducive to maintaining a healthy lifestyle. It is important to identify and address negative health behaviors in this population, not only in terms of personal health, but also in its effect on their interaction with future patient populations. The attrition of interest in prevention during undergraduate medical training is cause for concern; future clinical practice will be strongly motivated by their perceptions. Medical schools should identify health issues and assess preventive health perceptions among students in order to facilitate the adoption of preventive practices by future physicians. Medical Subject Headings (MeSH): health promotion, prevention, medical students, health behavior.