The effect of potential risk factors for multiple sclerosis was evaluated in a case-referent study that encompassed 83 cases and 467 randomized referents. Information on exposure was obtained by questionnaires that were mailed to the subjects. Mantel-Haenszel rate ratios were increased for males for occupational exposure to solvents and welding and for females for leisure time contact with dogs and caged birds. For both sexes, x-ray film examination occurred more frequently among cases than referents, possibly as an effect of early symptoms from the disease itself.