OBJECTIVE: To compare the suicide risk among Danish citizens with multiple sclerosis with that of the general population, and to evaluate changes over 45 years. METHODS: The study was based on linkage of the Danish Multiple Sclerosis Registry to the Cause of Death Registry. It comprised all 10,174 persons in whom multiple sclerosis was diagnosed in the period 1953 to 1996. The end of follow up was 1 January 1999. Standardised mortality ratios (SMRs) were calculated for various times after diagnosis and for age and calendar period of diagnosis. RESULTS: In all, 115 persons (63 men, 52 women) had taken their own lives, whereas the expected number of suicides was 54.2 (29.1 men, 25.1 women). Thus the suicide risk among persons with multiple sclerosis was more than twice that of the general population (SMR = 2.12). The increased risk was particularly high during the first year after diagnosis (SMR = 3.15). CONCLUSIONS: The risk of suicide in multiple sclerosis was almost twice as high as expected more than 20 years after diagnosis. The excess suicide risk has not declined since 1953.