As the prevalence of complementary and alternative medicine (CAM) use increases in the general population, it is critical that medical students are knowledgeable about its appropriate use and effectiveness. The purpose of this study was to describe osteopathic medical students' opinions, knowledge, perceptions, and perceived effectiveness of complementary and alternative medicine. A comprehensive review of the literature revealed only five studies of medical students. All of the studies to date included allopathic rather than osteopathic medical students.;The data were collected using a 72 item, closed format survey instrument. The survey was distributed to second year students at two osteopathic medical schools. A cross-sectional self-selected sample was utilized. The analysis of data included descriptive statistics, frequencies, and t-tests. A correlation analysis and factor analysis was also conducted.;It was found that participants had generally positive attitudes about the usefulness of CAM and the need for physicians to know more about CAM. Participants reported they were less than knowledgeable about most CAM therapies; however, the more they knew about a select therapy, the more effective they thought the therapy was. Participants' lack of knowledge about CAM therapies may explain why the conceptual groupings expected in the factor analysis did not occur. There were virtually no differences in results by gender.;Knowing more about students' opinions, knowledge and perceived effectiveness about CAM supports the need for curricular change. Adding content to medical school curricula related to the social and behavioral aspects of health will further develop medical student competencies in CAM. The development of competencies related to social and behavioral health will improve physician/patient communication which will ultimately improve patient outcomes.