High levels of prostatic zinc are associated with prostatic antimicrobial activities and are depressed in patients with chronic prostatitis. We investigated the inhibition of bacterial growth in the rat prostate with chronic prostatitis after intraprostatic injection of zinc and compared two different types of zinc delivery. Ninety male Wistar rats were used in the study. Experimental chronic bacterial prostatitis was induced by instillation of bacterial suspension (Escherichia coli 10(8) per ml) into the prostatic urethra. Animals were followed for 4 weeks and then injected intraprostatically with either 0.2 ml of zinc liposome (ZL) or zinc solution (ZS) (0.04 M zinc sulphate) or 0.2 ml of phosphate-buffered saline (PBS) for the controls. Ten rats in each group were sacrificed 4, 6 and 8 weeks after injection. The inhibition of inflammation and its consequences were analyzed microbiologically and histologically. Prostatic zinc concentrations were measured by inductively coupled plasma atomic emission spectrometry. Microbiological culture of the prostates demonstrated bacterial growth inhibition by the intraprostatic injection of zinc. The average infection rates and mean log(10) cfu/g of the zinc-treated groups were significantly lower than those of the controls. The histopathology showed resolving prostatitis in zinc-treated groups compared with the controls. Prostatic zinc levels were higher in the zinc-treated groups than in the controls 4 and 6 weeks after zinc injection (P<0.05). However, the ZL and ZS groups were found to be effectively identical in terms of prostatic zinc levels, bacterial cfu, and histological findings throughout the experiment period. The intraprostatic injection of zinc inhibited bacterial growth by increasing zinc levels in the rat prostatitis model. Our results suggest that the local application of zinc to the prostate may be a new treatment for chronic bacterial prostatitis at the point of its pathogenesis.