OBJECTIVES: It has been stated that lower urinary tract symptoms (LUTS) do not affect sexual function to any significant degree, but a recent study has suggested that there might be an association in men. The present study was conducted to investigate the relationship between LUTS and sexual problems in both men and women aged 40-65 years. METHODS: The survey was conducted in Denmark between May and June 2003. Detailed questionnaires were mailed to a random sample of 15,000 men and women aged 40-65 years. LUTS and sexual function were assessed by validated symptom scales. Multivariate regression analysis was performed using logistic regression for dichotomous dependent variables of sexual function. The independent variables for both sexes were age, LUTS, partner status, body mass index (BMI), alcohol consumption and co-morbidities. RESULTS: A total of 15,000 questionnaires were mailed out, 8491 were completed and returned, and 7741 were deemed valuable and included in the analysis. LUTS and sexual dysfunction were common in both men and women. Logistic regression analysis of items related to erection problems and satisfaction with sex life in men and sexual function in women showed that LUTS are an independent risk factor for sexual dysfunction in both men and women aged 40-65 years. Significant effects on sexual function were also found for the independent variables of partner status and co-morbidities. CONCLUSIONS: The presence of LUTS is an independent risk factor for sexual dysfunction in men and women. These results highlight the clinical importance of evaluating LUTS in patients with sexual dysfunction, and the need to consider sexual issues in the management of patients with LUTS.