The results of these clinical trials over the past 12 years have revealed an unsuspected toxicity of DES used in treating patients with cancer of the prostate when given in a dose of 5.0 mg daily. The first VA study did not show that orchiectomy was superior to estrogen in treating cancer of the prostate or that the combination orchiectomy plus estrogen had much to offer beyond the benefits of estrogen alone when indicated. The preponderance of evidence from the second study shows that 1.0 mg of DES appears to be about as effective as the 5.0 mg dose in treating cancer of the prostate but does not carry the excess hazard of cardiovascular deaths. Our overall recommendation at present is that patients with prostatic cancer should not be treated until their symptoms require relief, and at that time we recommend starting treatment with 1.0 mg DES daily. These recommendations may change as we continue to analyze our data.