We performed ten plasma perfusion (PP) treatments on eight patients affected by Myasthenia Gravis (MG) with high serum levels of autoantibodies against acetylcholine receptors (anti AChR-AB), and one PP treatment on a patient with MG of probable genetic origin and without specific antibodies. All patients (Osserman group III-IV) had undergone thymectomy and immunosuppressive therapy. Each patient received a treatment cycle of six PP sessions. Clinical conditions were assessed before and after the treatment with evaluation of muscular strength, ventilatory function, and electromyographic testing. Immunologic markers were tested before and after each PP. The patient without specific antibodies showed no improvement with PP and was excluded from our study. All the other patients showed continued improvement, with increased muscle strength and improved respiratory function. Four patients (follow-up 16-24 months) still maintain the clinical improvement; two, unexpectedly relapsed 11-12 months after PP, received a new treatment successfully (follow-up 9-10 month).