The rat prostate is innervated by pelvic and hypogastric nerves through a single pelvic ganglion, removal of which would result in complete denervation of the prostatic complex. The present study was conducted to investigate the effect of denervation on the rat prostate. Adult Sprague-Dawley rats of 300 g in body weight were divided into two groups. Bilateral pelvic ganglion denervation was performed in one group of animals; the other group received a sham operation. Three weeks later, animals were killed; and the ventral prostates were removed, weighed, and subjected to routine procedures for light and electron microscopy. The average weight, total protein content, and total content of acid phosphatase of the ventral prostates in the denervated group were significantly less than those in the control group. Total DNA content per prostate, however, was not significantly different between the two groups. Results of histological examination indicated that the prostates from control animals showed normal morphology, whereas those from the denervated animals showed reduced cell height and enlarged vacuoles surrounding the nuclei. Inspection of electron micrographs revealed that the prostates from denervated animals, compared with those of controls, showed a reduced ratio of cell height:cell width, which is associated with a reduced number of microvilli and secretory granules. These results indicate that denervation in the prostate is associated with a lower prostatic weight, decreased cell height, and reduced secretory activity.