Objective: To evaluate disability and prognosis in an untreated population-based incidence cohort of multiple sclerosis (MS) patients. Methods: The Expanded Disability Status Scale (EDSS) score was recorded in 220 MS patients. Disease progression was assessed by life table analysis with different endpoints and multivariate Cox regression analysis was performed for evaluation of prognostic factors. Results: The probability of being alive after 15 years was 94.8+1.8% (s.e.), of managing without a wheelchair (EDSS57.0) 75.8+3.2%, of walking without walking assistance (EDSS56.0) 60.3+3.6%, and of not being awarded a disability pension 46.0+3.7%. The probability of still having a relapsing-remitting (RR) course after 15 years was 62.0+4.1%. A RR course and long interval between the initial (onset) and second episode (43 years) predicted favorable outcome. There was also a trend towards favorable outcome in patients with optic neuritis, sensory symptoms and low age at onset, but these factors were associated with the RR course. Motor symptoms and high age at onset indicated unfavorable outcome, but these factors were associated with the primary progressive course. Conclusions: A RR course and long inter-episode intervals in the early phase of the disease were associated with a better outcome. Other onset characteristics indicating a favorable outcome were associated with the RR course while characteristics indicating an unfavorable outcome were associated with the PP course.