Thirty men having Parkinsons disease (PD) and 30 controls were studied prospectively by the use of the International Index of Erectile Function (IIEF) to assess erectile dysfunction (ED). Of the patients with PD (mean age of 59 years), 46.66% referred to the practice of sexual activity. All of the parkinsonians were using antiparkinsonian medication. In the control group (mean age of 63 years), 76.66% referred to the practice of sexual activity, 46.60% to arterial hypertension and 6.66% to diabetes mellitus. The median score for the PD group according to the IIEF was 34, and that for the controls 50. The main differences between the two groups were in the erectile function, orgasmic function and satisfaction with the sexual relationship. The IIEF is a multidimensional scale widely accepted to assess the ED. The data obtained suggest that ED is more frequent among parkinsonians and points out to the role of DP in the genesis of ED.