We evaluated, by qualitative and quantitative methods, the structural alterations in the bladder wall of rats submitted to surgical castration, as well as the role of hormone replacement in reversing the possible structural alterations. Twenty-four 12-week-old male Sprague-Dawley rats were used. The animals were divided into 3 groups comprising 8 animals each and treated as follows. Members of group CONTR (control) underwent a sham operation only and were sacrificed after 2 months. Members of group ORCH (orchiectomy) underwent bilateral orchiectomy and were sacrificed after 2 months. Members of group ORCH+TEST (testosterone) underwent orchiectomy, received testosterone replacement after 1 month, and were sacrificed 1 month later. We performed a qualitative and quantitative analysis of collagen by light microscopy, scanning electron microscopy, biochemistry, and a histomorphometric analysis of smooth muscle and elastic fibers in the 3 groups. The results showed a significant decrease in absolute values of elastic fibers in the castrated group. The histomorphometric analysis of epithelial height did not show differences among the groups. There was no statistical difference in quantitative analysis of collagen, either by histomorphometry or by biochemistry. Also, there was no difference in the smooth muscle cells. However, the qualitative analysis revealed differences in collagen (castrated group) when compared with controls and with rats submitted to hormone replacement. Hormone replacement with testosterone was able to revert the alterations observed. The findings suggest that hormone replacement, even when instituted at a late stage, is effective in reversing the bladder wall alterations produced by secondary hypogonadism.