The diagnosis of multiple sclerosis remains a clinical one. It is based on the documentation of lesions at two or more sites of the CNS and of two or more relapses in relapsing-remitting disease, or persistent deterioration for 6 months in primarily chronic-progressive disease. Because no symptom and no result of a paraclinical investigation is specific enough, a careful differential diagnostic work up by a physician competent in clinical neurology is essential. CSF examination, blood serology, MRI and in some cases evoked potentials may help in this work-up. The results of recently completed controlled trials suggest that, besides high dose steroid treatment of acute relapses, immunomodulatory treatments may help to improve the prognosis in relapsing-remitting phase of the disease. Treatments that will enter clinical practice in the next year or two are recombinant interferon beta-1b and -1a and perhaps copolymer 1. Non-selective immunosuppressants (azathioprine, in more severe cases other substances with more intensive cytostatic activity) also have a place in selected cases. The efficacy of such treatment in secondary chronic-progressive disease as well as the indication for very early treatment are now under investigation. Some possible future developments in diagnosis and therapy of MS are discussed.