Objective To investigate the effect of N\+w-nitro-L-arginine-methyl-ester(L-NAME) on spermatogenic cell apoptosis and the expression of Bax in rats experimental cryptorchidism. Methods Unilateral cryptorchidism was surgically induced in the rats under pentobarbital anaesthesia. The rats of cryptorchid +normal saline group and cryptorchid+L-NAME group were injected intraperitoneally normal saline and L-NAME ［50mg/(kgI>&#/I>8226;d)］ accordingly. The activity of NOS in the left testis was measured by colorimetric method on the 7th day after operation. The effect of L-NAME on apoptosis of spermatogenic cell in the unilateral cryptorchidism was evaluated by TUNEL and FCM .The mRNA and protein expression level of Bax in testes was detected by RT-PCR and immunohistochemieal assay accordingly. Results Administration of L-NAME could attenuate the activity of NOS and inhibit spermatogenic cells apoptosis in rats experimental cryptorchidism, and it could significantly inhibit weight loss of the cryptorchid. The mRNA and protein expression level of Bax in the cryptorchid testes treated with L-NAME was the lowest among the four groups, and in the testes of the cryptorchid group and the cryptorchid +normal saline group the mRNA and protein expression level of Bax was higher than that of sham operation group. Conclusion The mRNA and protein expression level of Bax in rats experimental cryptorchidism increases significantly. Administration of L-NAME can inhibit spermatogenic cell apoptosis by decreasing Bax expression.