Prostatic tissue levels of Cefoperazone (CPZ) were studied after the administration of 3 g of CPZ, in 16 patients with prostatic hypertrophy who underwent retropubic prostatectomy. The CPZ concentration in the surgical capsule at 60 min. after the administration of CPZ was about 2 times higher than that in the gland. As compared with the histological type of removed gland, the levels in the glandular hyperplasia were slightly higher than that in the fibromuscular and mixed type hyperplasia, but the difference was not statistically significant. CPZ was found to be effective for the treatment of post-operative and bacterial prostatitis, since the CPZ levels of prostatic tissue were considerably high and above the minimal inhibitory concentration level for most bacteria.