A group of 16 patients with secondary chronic progression of multiple sclerosis treated by short-lasting intensive immunosuppression (cyclophosphamide with ACTH) by the programme of Hausser et al (4) was compared with a clinically similar group of 16 patients treated exclusively with intramuscular ACTH. During 2 years of observation of the patients it was observed that short-lasting intensive immunosuppression induced with simultaneous administration of cyclophosphamide and ACTH had no beneficial effect on the slowly progressing form of multiple sclerosis. The observation leads to the conclusion that cyclophosphamide therapy should not be used in view of absence of favourable effect on the course of multiple sclerosis and the risk of increased frequency of malignant neoplasms which cannot be ruled out in this method.