AbstractBecause of the growing interest in prospective trials of dietary and chemopreventive interventions for cancer, we studied the characteristics of persons likely to participate in such investigations. The study population consisted of a random sample of 576 persons who had previously attended the Prevention‐Detection Center at Roswell Park Memorial Institute to receive a cancer screening examination and a risk assessment. Data were collected using a mailed questionnaire. Of the respondents, 77% indicated some degree of interest in participating in a cancer prevention study involving dietary changes, 27% indicated a definite interest and 50% indicated a possible interest. A similar pattern of response was obtained with respect to participation in a cancer prevention study that involves subjects taking medication, such as vitamin supplements. The findings suggest that those who are the most interested in participating in cancer prevention research are more likely to (on average) a) be younger, b) better educated, c) have higher annual family incomes, d) be regular vitamin users, e) have greater awareness of the possible link between dietary practices and cancer risk, f) be more concerned about getting cancer, and g) be more likely to believe that changes in dietary practices can decrease the cancer risk. These findings may have important implications for the planning and conduct of prospective trials of cancer prophylaxis.