The present study was undertaken to evaluate the penetration of Ceftazidime (CAZ) into prostatic tissue (P) and serum (S). Thirty-seven patients with benign prostatic hypertrophy took part in this study. CAZ was administered intravenously at a dose of 1g preoperatively. Blood samples were taken simultaneously at the time of tissue sampling by transurethral resection of the prostate (TUR-P). The patients were divided into 3 groups. In group 1 (twelve patients), intravenous injection of the drug was given 60 minutes before tissue sampling. The mean concentrations of CAZ were 23.4 +/- 7.4 micrograms/g in the prostatic tissue and 45.0 +/- 15.9 micrograms/ml in the serum. In group 2 (thirteen patients), the injections were given 120 minutes before tissue sampling. The mean concentrations of CAZ were 18.0 +/- 8.2 micrograms/g in the prostatic tissue and 39.8 +/- 21.3 micrograms/ml in the serum. In group 3 (twelve patients), the injections were given 240 minutes before tissue sampling. The mean concentrations of CAZ were 11.3 +/- 3.2 micrograms/g in the prostatic tissue and 22.3 +/- 9.6 micrograms/ml in the serum. These findings indicate that CAZ is useful for the treatment of prostatitis and preventive medication before TUR-P.