OBJECTIVE: Physical disability explains only part of the reduced quality of life found among multiple sclerosis (MS) patients. Bladder dysfunction and sexual disturbance are frequent and distressing problems for MS patients. We therefore estimated the relationship between the presence and degree of sexual disturbance/bladder dysfunction and the patients' quality of life as measured by the SF-36 Health Survey. METHODS: We performed a cross-sectional study of all individuals with the onset of MS between 1976 and 1986 in Hordaland County, Norway. The disease duration at examination was 9-19 years; 194 patients (94%) participated. RESULTS: Fifty-three per cent of the patients with low physical disability (Expanded Disability Status Scale (EDSS) 4.0) were 86 and 81% respectively. The patients with sexual disturbance had markedly and significantly reduced scores on all eight SF-36 scales, this was after adjustment for disease development measured by the EDSS. The patients without sexual disturbance scored 0.5 s.d. lower than a normal population on the social functioning scale, whereas those with marked sexual disturbance scored 1.5 s.d. lower. Similar results were found for the patients with bladder dysfunction. CONCLUSION: Bladder and sexual problems are associated with a marked reduction in the quality of life, also among patients with otherwise low disability. This underlines the need for identifying and treating these problems.