OBJECTIVE To explore the penetrability and therapeutic effect of vancomycin to the prostates of rats with bacterial prostatitis (BP) or benign prostate hyperplasia (BPH)-BP. METHODS The experimental rats with BP or BPH-BP were injected with vancomycin through the tail vein. The prostate tissues and sera were isolated respectively from the rats at 10 min to approximately 24 h after treatment and the antibiotic activities of the samples were detected by serial dilution test and agar diffusion test. The rats with BP or BPH-BP were treated with vancomycin by intravenous injection daily for 5 days. The prostates were collected the second day after injection and bacteria were isolated and determined. One to five weeks after treatment, the prostates of the animals were isolated and pathologic tests were done. RESULTS No bacteria could be isolated from the prostates of the normal rats, but positive isolation was achieved from the prostates of the infected animals 28th day after infection. In the first 4 days after treatment, a decrease of bacteria could be detected in the prostate samples of the rats treated with BP or BPH-BP. After 5th day, no bacteria could be detected from 91.7% prostates of the treated groups. Obvious antibiotic activity in both sera and prostates could be detected 10 to approximately 150 min after the antibiotic injection. Antibiotic activity of the prostate tissues could be lower or higher than or equal to that of the sera in the same period. Pathologic tests detected obvious exudation and leukocyte invasion in the prostate tissues of the BP rats and gland proliferation in the BPH rats. Vancomycin treatment and the consequent reduction of bacteria obviously alleviated the inflammatory pathological changes in the prostates of the BP rats. CONCLUSION Vancomycin given intravenously has more penetrability to the prostates of either BP or BPH-BP rats. The antibiotic concentration in the prostate tissues may be equal to or higher than that of the sera, so that the susceptive bacteria in the prostates will be killed and the alleviation of the inflammation and repair of the tissues accelerated effectively.