We estimated survival probability and excess death rates for patients with MS on the basis of data from the Danish Multiple Sclerosis Registry, which includes virtually all patients diagnosed with MS in Denmark (population, five million) since 1948. We reviewed and reclassified all case records according to standardized diagnostic criteria. By linkage to the Danish Central Population Registry, we lost to follow-up only 25 patients who had emigrated. The median survival time from onset of the disease was 28 years in men (compared with 40 years in the matched general male population) and 33 years in women (versus 46 years). The median survival time from diagnosis was 22 years in men (versus 37 years) and 28 years in women (versus 42 years). The excess death rate between onset and follow-up (observed deaths per 1,000 person-years minus the expected number of deaths in a matched general population) was 14.3 in men, which was significantly higher than in women (12.0). Excess mortality increased with age at onset of MS in people of each sex. The 10-year excess death rate has decreased significantly in recent decades. Excess mortality was highest in cases with cerebellar symptoms at onset.