Aims of the study: Regulation of the penile smooth muscle tone and contractility is closely related to the activity of vasoactive substances, angiotensin II or nitric oxide. We investigated the relationship between gene polymorphism in the angiotensin converting enzyme (ACE) or endothelial nitric oxide synthase (ecNOS) and development of erectile dysfunction. Methods: In 84 subjects with organic erectile dysfunction and 63 control subjects, gene polymorphisms in the ACE and ecNOS were determined by the polymerase chain reaction (PCR). Results: The DD genotype of ACE was significantly (P < 0.01) more frequent in subjects with organic erectile dysfunction (54%) than in control subjects (24%). There was no significant difference in the distribution of the genotypes of ecNOS. Conclusion: The deletion polymorphism in the ACE gene, the DD genotype, as a marker of general vascular disease, may be seen more frequently in men with a diagnosis of vasculogenic erectile dysfunction.