The clinical efficacy of norfloxacin (NFLX) was evaluated on 40 patients. They had subjective symptoms suggestive of prostate inflammations and more than five white blood cells (WBC)/hpf in their prostatic secretions (EPS) or VB3. Of these, gram negative rods were isolated from the EPS in 3 patients and gram positive cocci were obtained in 26 patients. The overall clinical efficacy was determined at the second week. The effectiveness rate of the subjective symptoms was 82.5%. The effectiveness rate of the WBC in the EPS was 47.4%. The effectiveness rate of the bacteria in the EPS was 64.3%. The overall clinical effectiveness rate was 77.8%. A subjective side effect was observed only in one patient who had skin eruption like urticaria. Mild liver dysfunction of blood chemistry analysis was shown only in two patients but they had had long standing chronic hepatitis. We conclude that NFLX is an effective drug for the patients with chronic prostatitis.