A chemoprevention trial in prostate cancer would be a formidable but potentially rewarding study. The current status of knowledge of drug interactions with, biomarkers of, and even the natural history of prostate cancer is insufficient to study all levels of men at risk. Currently, the most promising group to study is group I--those men with a high probability of developing prostate cancer but who do not currently have evidence of the disease. This could be a placebo-controlled, prospective and randomized study with the endpoint being clinically-detected prostate cancer. In addition, much may be gained from short-term pilot studies of "chemo-active" agents on morphologic and other biomarkers of prostate cancer initiated immediately before surgical removal. It is hoped that such studies may provide rationale for future efforts directed at preventing progression of premalignant or early prostate cancer lesions.