Abstract: This study will explore the changes of endothelial nitric oxide synthase (eNOS) and inducible nitric oxide synthase (iNOS) expression in spermatogenic cells and the change of level of nitric oxide (NO) in adult male hamster testes during diethylstilbestrol (DES) inducing spermatogenesis apoptosis. The study will be helpful for illustrating the mechanism of DES induced adult animals spermatogenesis apoptosis. Adult male hamsters were treated daily with olive oil vehicle either alone (control) or containing various doses of DES (0.01,0.1 and 1mg/kg body weight, respectively) (experiment) by subcutaneous injection for 7 days. The levels of NO in testes were measured. The expressions of eNOS and iNOS proteins in the testes seminiferous tubules were detected by immunohistochemistry. The changes on the histological morphology of spermatogenic cells were observed by electron microscope. The apoptotic spermatogenic cells were detected by TUNEL staining. The change of the distribution of lipid droplets in seminiferous tubules were observed by Sudan Ⅲ staining. Results show that the level of NO was dose-dependent on DES. The apoptotic level of spermatogenic cells was similar to the level of expression eNOS and iNOS of spermatogenic cells, and these spermagenic cells were main spermatocytes and round spermatids. There are lots of marrow-like structure in degenerating spermatogenic cells cytoplasm. Lots of lipid droplets local between or in spermatogenic cells.