Bicalutamide (Casodex) has been approved as a new option for the treatment of prostate cancer. It is a new non-steroidal anti-androgen synthesized by the British company Zeneca. In pharmacological studies using rats and other subjects, the product showed excellent affinity with androgen receptors and was found to be anti-androgen active and effective against tumors, and so clinical trials have begun. Approval has been obtained in approximately 70 countries, including the United Kingdom, the United States and Germany. Anti-androgens are used extensively in combination with LHRH analogs or surgical castration (MAB therapy) in the treatment of prostate cancer. Overseas, encouraging results have been obtained from comparative trials using bicalutamide or flutamide in MAB therapy. Bicalutamide is expected to be highly effective. Moreover, it can be administered in a once-daily dose, which is expected to improve patient compliance. In a late Phase II study in Japan, a response rate as high as 64.4% was achieved when bicalutamide was administered alone. The potential for bicalutamide to be used alone is important because of the growing emphasis on patient quality of life and sexual function in prostate cancer therapy.