• This review of research on affective disorders in multiple sclerosis was prepared by members of the Cognitive Function Study Group of the National Multiple Sclerosis Society (New York, NY) to call attention to the prevalence and seriousness of emotional disturbances in multiple sclerosis, and to encourage further investigation of these syndromes. We present English-language studies of euphoria, pathological laughing and weeping, depression, and bipolar disorder, describe methodological limitations, and suggest areas for future clinical research.