BACKGROUND In the past decade good therapeutic results have been reported with high dosage of intravenous immunoglobulins (Ig i.v.) in various autoimmune disorders, including myasthenia gravis (MG). Plasmapheresis has been used successfully in this disorder on indications similar to those described for the use of Ig i.v.. We have used sequential treatment of plasmapheresis followed by high doses of intravenous gammaglobulin in MG, seeking complementary benefits from the two kinds of treatment. METHODS The sample included 10 patients with MG (7 of Osserman's grade II-B, 1 of II-A and 2 of III). We began treatment with plasmapheresis, and then continued with an i.v. infusion of Ig at a dose of 400 mg/Kg/day for 5 days. To evaluate the response to treatment, we used the classification system for muscle weakness based on the Virginia University modification of Osserman's grades, on the clinical involvement grade scales and on functional activity. RESULTS All patients showed statistically significant improvement of the parameters studied. Improvement started between the first and sixth day, following administration of Ig i.v. and persisted for the following 16 weeks. CONCLUSIONS We consider that combined treatment with plasmapheresis and Ig i.v. may synergically potentiate the immunological effects since they have different mechanisms of action. The indication for this is limited to serious clinical conditions resistant to other treatment, to speed recovery.