The plasma concentration of asymmetrical dimethylarginine (ADMA), an inhibitor of nitric oxide synthase, has been linked to endothelial dysfunction. We investigated the relation between ADMA, symmetric dimethylarginine (SDMA) and L-arginine concentrations and erectile dysfunction. We compared plasma levels of ADMA, SDMA and L-arginine in 61 men in good health with erectile dysfunction of arteriogenic and non-arteriogenic origin. Diagnosis of erectile dysfunction was based on the International Index of Erectile Function Score and its aetiology was classified with penile echo-colour-Doppler in basal condition and after intracavernous injection of prostaglandin E1. The ADMA and SDMA concentrations were significantly higher in men with arteriogenic erectile dysfunction compared with those with erectile dysfunction of non-arteriogenic origin (p < 0.05) and the concentrations in both subgroups were significantly higher than in controls (p < 0.001). There was a negative correlation between ADMA and International Index of Erectile Function Score only in arteriogenic erectile dysfunction subgroup. L-arginine did not differ significantly neither between the two erectile dysfunction subgroups (p > 0.05) nor between each of the two erectile dysfunction subgroups and controls (p > 0.05). The L-arginine/ADMA and the L-arginine/SDMA ratios in arteriogenic erectile dysfunction subgroups were significantly lower than both in controls (p < 0.05) and in non-arteriogenic erectile dysfunction patients (p < 0.05); the two ratios in non-arteriogenic erectile dysfunction patients did not differ from those in the controls (p > 0.05). We conclude that ADMA and SDMA concentrations are significantly higher and L-arginine/ADMA ratio lower in patients who have arteriogenic erectile dysfunction compared with both patients with non-arteriogenic erectile dysfunction and controls. The negative correlation between ADMA and severity of erectile dysfunction is present only in patients with arteriogenic erectile dysfunction. This study supports the importance to always distinguish arteriogenic from non-arteriogenic erectile dysfunction patients to study the complicate erectogenic mechanisms that lead to erectile dysfunction and also to provide potential therapeutic agents for patients with arteriogenic erectile dysfunction.