The important progress achieved in the treatment of prostate cancer comes by exacting significant costs [11, 16-18, 20, 23, 25]. Currently, there is incomplete evidence that the radical interventions at hand significantly reduce the human costs of the disease. Surgery and radiotherapy induce substantial risks of incontinence and impotence. The PSA test has probably decreased the stage at which prostate cancer is diagnosed [15]. Nonetheless, the PSA is a means of earlier detection; it does not elucidate quantitatively distinct modes of treatment. The PSA test is not a means of prostate cancer prevention. The continuing incidence, morbidity, and mortality imposed by this disease strongly indicate that preventive strategies for its control are necessary. Chemoprevention with selenium and other agents offers a promising approach that is undergoing intensive investigation. Randomized trials underway at the authors' center are building on the important clinical trial results reported by Dr. Larry C. Clark. These studies will evaluate the activity of selenium at several points along a continuum ranging from cancerous prostatic tissue in men with diagnosed cancer to premalignant tissue in men with high-grade PIN to healthy tissue in high-risk men with negative biopsy to long-term effects on cancerous tissue in men with frank cancer. These trials will also offer an opportunity for preliminary evaluation of the mechanisms by which selenium treatment could result in the slower development or progression of prostate cancer.