Erectile dysfunction frequently occurs with diabetes mellitus. A survey of diabetic men was conducted by anonymous questionnaire to investigate the associations of erectile dysfunction with various predictive factors. A total of 112 diabetic males without an obvious history of erectile dysfunction were available for analyses. The mean age and duration of diabetes were 53.7 +/- 12.2 years and 10.2 +/- 8.6 years (mean +/- standard deviation), respectively. The questionnaire included questions on the presence or absence of smoking, hypertension, libido and subjective symptoms of diabetic neuropathy that may be associated with erectile dysfunction. Analysis of the answers to the questionnaire revealed that 40% of the patients complained of erectile dysfunction (erection 'always insufficient'). Erectile dysfunction was significantly correlated with age (p = 0.005), but not with duration of diabetes (p = 0.25), adjusted for age. Erectile dysfunction was also associated with sensory neuropathy and reduced libido, independently of age. The logistic regression analysis revealed that erectile dysfunction was positively associated with reduced libido and age. The odds ratio of erectile dysfunction for reduced compared to unreduced libido was 18.21, suggesting that psychogenic factors have a marked influence on erectile dysfunction. It is concluded that the presence of erectile dysfunction should be considered when symptoms related to diabetic neuropathy are observed; psychological approaches, such as sexual counseling, could be applied for the treatment of erectile dysfunction.