The aim of this study was to investigate penile microcirculation in patients with erectile dysfunction. Laser doppler flowmetry was performed in 67 patients (mean age 43.9 +/- 1.53 years) with organic erectile dysfunction and in 20 men without erectile dysfunction. It was found that in patients with arteriogenic erectile dysfunction blood flow parameters were subnormal including flux motions. The occlusive test revealed reduced postocclusive reactive hyperemia in patients with arteriogenic erectile dysfunction. Patients with neurogenic erectile dysfunction have signs of sympathetic denervation of microcirculation and decreased respiratory response.