To determine if such factors as first symptom, sex, age at onset and initial clinical course have any influence on life expectancy of multiple sclerosis patients, a survival analysis from date of diagnosis for 598 MS-patients in Norway was performed. To study the effect of all the variables simultaneously we used the Cox proportional hazards regression model with incomplete data. Median survival time was 27 years after diagnosis. The variable which most strongly predicted the duration of the disease was age at onset. High age at onset and a progressive course of the disease were correlated with a more unfavourable prognosis. The onset symptom, vertigo, was also correlated with a shorter life expectancy. No significant effect of sex was found. We found in this material an indication of improved survival over the study period.