Objective To study the effect of hypertension on inducible isoform of nitrogen oxide syntheses (iNOS) expression and reproductive function in testes of Dahl hypertensive rats Method The iNOS expression in Dahl rat testes was localized and assayed semi-quan titatively by immunohistochemistry.Results iNOS was expressed and localized predominantly in the cytoplasm of Sertoli and Leydig cells in both normal and hypertensive rats. However, in the early stage of hypertension, the expression of iNOS was stronger in testes than that of the normal rats (P＜0. 05). With the development, the staining intensity of iNOS decreased gradually in the late stage. Moreover, the level of testosterone decreased with the increase of blood pressure. But in vitro, there was no difference in the expression of iNOS between cultured Sertoli cells from normal rats and hypertensive rats.Conclusion High-salt food induced hypertension in Dahl rats, which was characterized by the high expression of iNOS in rat Sertoli and Leydig cells; excessive NO produced by iNOS reduced the level of testosterone in testicle artery, and may thus affect the reproductive function of rats testis.