The objective of this study was to validate the German translation of the International Index of Erectile Function (IIEF). The IIEF was administered to 59 patients with erectile dysfunction (ED), to 38 patients with Peyronie's disease and to 33 controls. All patients were investigated by standardized German versions of international questionnaires of anxiety, depression, social desirability, quality of partnership, physical complaints and life-satisfaction. The five subscales of the English version, however, could not be replicated. Internal consistency for the complete questionnaire of 15 items was high (Cronbach's alpha=0.95). Based on the total scale and two subscales, we were able to discriminate sexual function between the ED group and the comparison groups. There was no significant correlation between the IIEF scores and anxiety, depression, somatic complaints and life-satisfaction. The German version of the IIEF has found good comprehension, and acceptance by the majority of patients. Its use is somewhat limited by its focus on sexual activity in partnership. In contrast to the English version, it mainly addresses a single factor of sexual function.