The present study was undertaken to evaluate the penetration of ofloxacin into prostatic tissue. Thirty-one patients with benign prostatic hypertrophy were entered in the study. Ofloxacin was administered orally in a dose of 200 mg three times daily for 3 days preoperatively. Blood samples were taken simultaneously at the time of tissue sampling. The patients were divided into 2 groups. In group 1, tissue sampling was done about 17 hours after the final drug administration. The mean concentration of ofloxacin was 6.88 +/- 3.98 micrograms/g in prostatic tissue and 2.14 +/- 0.81 micrograms/ml in serum. In group 2, sampling was done 5.5 hours after the final administration. The mean concentration of ofloxacin was 6.73 +/- 2.99 micrograms/g in prostatic tissue and 2.90 +/- 1.50 micrograms/ml in serum.