OBJECTIVE To evaluate the effects of the Chinese herbal formula Shuganyiyang (SGYY) capsule on arteriogenic erectile dysfunction (ED) in a rat model and to investigate the underlying molecular mechanism. METHODS Forty male Sprague-Dawley rats were subjected to bilateral ligation of the internal iliac artery and then divided into 4 groups (n = 10 per group). They were treated daily with either sildenafil (10.5 mg/kg), or SGYY at 1 of 2 dosages (1 g/kg and 0.5 g/kg) for 30 days. Erectile function was evaluated using cavernous nerve electrical stimulation after treatment, and the cavernous tissue specimens of all animals were harvested for gene and protein examination using real-time reverse transcriptase polymerase chain reaction, Western blot analysis, and cyclic guanosine monophosphate (cGMP) measurement. RESULTS The ratio of the maximal intracavernous pressure to the mean arterial pressure was significantly higher in the SGYY (1 g/kg and 0.5 g/kg) rats than that in the models (P < .01). The gene and protein expression of 3 subtypes of nitric oxide synthase (NOS)-neuropathic (nNOS), inducible (iNOS), and endothelial (eNOS)-and cGMP concentrations in cavernous tissue in SGYY-treated rats were significantly higher than in the models. However, phosphodiesterase type 5 (PDE5) expression in the SGYY rats was lower than those in models (P < .01 or P < .05). CONCLUSION SGYY significantly improves the maximal intracavernous pressure in arteriogenic ED in a rat model. The underlying mechanism of action of SGYY involves increasing the expression of some main factors in the NOS-cGMP pathway and reducing the expression of PDE5. UROLOGY 79: 241.e1-241.e6, 2012. (C) 2012 Elsevier Inc.