Objective To investigate the change of the number, morphology and function of Leydig cells after induction of cryptorchidism. [WTHZ]Method Adult rats were induced cryptorchidism by confining the testes of both sides into the abdominal cavity. They were decapitated at intervals of 3, 7, 20 and 28 days postoperation (6 rats in each group). Sham group as the control. The number and morphological changes of Leydig cells were detected by the method of stereology. Application of immunohistochemistry detected of the expression of cell division cycle 25 A （CDC25A）, stem cell factor （SCF）, androgen receptor （AR）, estrogen receptor α（ERα)in Leydig cells. [WTHZ]Result The volume fraction of testicular interstitium increased significantly, but the absolute volume of testicular interstitium unchanged after induction of cryptorchidism. The number and morphology of Leydig cells did not change significantly. Immunohistochemical staining showed CDC25A, SCF strongly expressed in the area of Leydig cells, and the cryptorchidism had no significant effect on their expression. AR had weak staining in the cytoplasm of Leydig cells, and the intensity of AR expression no significant changes between different groups. The expression of ERα in Leydig cells in the control group was weak, almost no positive nuclei. But the percentage of Leydig cells which has ERα positive nucleus increased significantly with the prolongation of cryptorchidism time. It had reached 93.6% after 28 days cryptorchidism. [WTHZ]Conclusion Experimental cryptorchidism has no s