Documented treatment for amyotrophic lateral sclerosis (ALS) is not available. Several studies have suggested an immunological etiology and an effect on the course of disease, when ALS-patients were treated with immunosuppressants. The aim of the present study was to evaluate the effect of immunosuppressive therapy in ALS-patients comparing the course of disease in treated patients and in historic controls with ALS; 21 patients were included in the study, 17 men and 4 women. Median age at admission was 54 years for men and 61 years for women. 5 had progressive bulbar palsy, 7 both upper and lower motor neuron affections and 9 progressive muscular atrophy. Patients were treated with prednisolone and azathioprine for 1 year and examined regularly; 12 were treated and followed for more than a year. No definite difference between survival in treated patients and their controls was found.