Erectile and endothelial dysfunction may have some shared pathways through a defect in nitric oxide activity. We evaluated associations between erectile function, endothelial function and markers of systemic vascular inflammation in 80 obese men, aged 35-55 yr, divided into two equal groups according to the presence/absence of erectile dysfunction. Compared with non-obese age-matched men [no.=50, body mass index (BMI)=24 +/- 1], obese men (all) had impaired indices of endothelial function as suggested by the reduced mean blood pressure and platelet aggregation responses to L-arginine, and higher circulating concentrations of the proinflammatory cytokines interleukin-6 (IL-6), interleukin-8 (IL-8), interleukin-18 (IL-18), as well as C-reactive protein (CRP). The mean erectile function score was 14 +/- 4 (range 7-19) in obese men with erectile dysfunction and 23.5 +/- 1 (range 22-25) in obese men without erectile dysfunction. Endothelial function showed a greater impairment in impotent obese men as compared with potent obese men. The mean blood pressure and platelet aggregation decreases following L-arginine were -1.5 +/- 1.1 mmHg and -1.1 +/- 1.2%, respectively, in obese men with erectile dysfunction, and -3.4 +/- 1.2 mmHg and -5.6 +/- 2.1%, respectively, in obese men without erectile dysfunction (p < 0.01). Circulating CRP levels were significantly higher in obese men with erectile dysfunction as compared with obese men without erectile dysfunction (p < 0.05). Erectile function score was positively associated with mean blood pressure responses to L-arginine and negatively associated with BMI, waist-to-hip ratio (WHR), and CRR Erectile and endothelial dysfunction associate in obese men and may contribute to their raised cardiovascular risk through impaired nitric oxide availability elicited by a low-grade inflammatory state.