A case-control study of multiple sclerosis (MS) has been carried out in western Norway. The study included 93% of the patients who had clinical onset of MS in the county of Hordaland during the years 1976-86 (N = 155) and 200 controls, marginally matched for age, sex and residence. There was no statistically significant difference between MS patients and controls with regard to exposure to organic solvents, exposure to the combination organic solvents and welding or to organic solvents and other chemical compounds.