Objectives: It is not yet certain whether early hormonal treatment in cryptorchidism is safe for germ cells. We investigated the histologic effects of human chorionic gonadotropin (hCG) therapy on descended testes of rats. Design and Setting: Thirty male Wistar albino rats were randomized into two groups. The rats of the hCG group (n = 15) were administered 50 IU/kg/day hCG once daily via the subcutaneous route for 15 days. Fifteen rats received subcutaneous isotonic saline and acted as controls. At the first month, testicular tissue was obtained after scarification in both groups. The histological examination was performed to evaluate the seminiferous tubular diameter, germinal membrane thickness, and the percentage of the open seminiferous tubule lumen in each testis to compare the two groups. Results: The percentage of the open seminiferous tubular lumen in testicular tissues of hCG-treated rats was higher than that of controls (p <0.05). The mean germinal membrane thickness in testicular tissues of the hCG group was statistically lower than that of the control group (p < 0.05). There was no statistical difference between mean seminiferous tubular diameter in testicular tissues of hCG-treated rats and controls, as expected (p > 0.05). Additionally, there were two interesting cases of Sertoli cell only appearance in the hCG group. Conclusions:We may assume that hCG impairs the seminiferous tubule histology in normal testes of rats. Thus, further experimental studies on dose dependency and the reversibility of these effects are warranted. Copyright (C) 2006 S. Karger AG, Basel.