A group of 16 patients with severe generalized myasthenia gravis (MG) (five with thymoma) that was resistant to anticholinesterases, thymectomy, and corticosteroids were treated by plasmapheresis. Twelve patients showed an excellent clinical response. Plasmapheresis is an effective treatment modality for many patients with severe generalized MG resistant to other forms of therapy. Unfortunately, the beneficial results are only transient and periodic plasmapheresis treatments are necessary.