Objective: To evaluate the effects of nicotine-and tar-free cigarette smoke extract on plasma testosterone level and erectile function in rats.Methods: Thirty male Sprague-Dawley(SD)rats were randomly divided into 3 groups(n=10): the control group(PBS group),fCSE group and antioxidant group(CSE ± GSH group).After 8 weeks,by electrostimulating of the cavernous nerve,maximal intracavernous pressure(MICP),mean arterial pressure(MAP),ICP/MAP,Tmax(the time of stimulating MICP happened),cavernosal filling rate(CFR)were measured with radioimmunoassay to evaluate the erectile function of rats;the levels of plasma testosterone(T)were measured with radioimmunoassay,the activity of superoxide dismutase(SOD),MDA,NOS,from cavernosal tissue homogenate was measured.To observe the morphological changes of corpus cavernosum tissue by Masson staining Results: Compared to the control group [T(5.37±1.43)μg/L,NOS(2.90±0.27)U/mg,SOD(18.41±1.09)U/mg prot],fCSE group [T(3.22±1.11)μg/L,NOS(1.67±0.18)U/mg,SOD(13.36±1.18)U/mg prot] decreased obviously.About index of erectile function,compared to the control group [MICP(85.92±6.36)mmHg,MICP/MAP(0.86±0.09)and CFR(2.14±0.44)],fCSE group [MICP(58.99±10.76)mmHg,MICP/MAP(0.56±0.08),CFR(0.89±0.44)] decreased obviously;and Tmax [(29.90±5.78)vs.(42.90±8.56)s] delayed obviously,and the levels of T were positively correlated with CFR(r=0.364,P<0.05).Compared with the control group,Masson staining showed that fCSE group of the fiber about corpus cavernosum smooth muscle tissue/collagen fiber decreased obviously [(+0.27 0.04)vs.(0.98+0.12)].Antioxidant group could improve index of erectile function,but there was no obvious effect in improving the ratio of the corpus cavernosum smooth muscle tissue/collagen fiber Conclusions: The decrease of nicotine-and tar-free cigarette smoke extract on plasma testosterone level and erectile function in rats was related to oxidative stress,Antioxidant therapy could improve erectile function,but it was limited in protecting penis organization.