Acute treatment of myasthenic crisis with immunoadsorption (IA) or plasma exchange is well established. The efficiency of chronic apheresis therapy in myasthenia gravis (MG), however, and its efficacy in reducing concomitant potentially harmful immunosuppressive therapy, is unknown. We treated 13 patients with therapy-resistant MG or severe steroid or azathioprine therapy-related side effects, or both, with long-term IA [median, 38 (range: 16-59) months]. IA was performed every second day until partial remission was achieved (modified Osserman score <2). Subsequently, oral immunosuppressive therapy was reduced and the frequency of IA adapted to the clinical symptoms. After initiation of IA the mean (SEM) Osserman score decreased from 3.23 +/- 0.12 to 1.23 +/- 0.08 within 1 month (P < 0.01). Mean azathioprine dose was reduced concomitantly from 89 +/- 9.4 mg/day to 56 +/- 11 mg/day (P < 0.05), and mean prednisolone dose from 41 +/- 7.6 mg/day to 22 +/- 8.5 mg/day (P < 0.05). After 36 months the number of IA-sessions/month had been reduced from 4.81 +/- 0.24 to 2.64 +/- 0.4 (P < 0.05), the mean azathioprine dose to 25 +/- 17 mg/day and the mean prednisolone dose to 9 +/- 3.6 mg/day. Six out of thirteen patients were weaned from IA after a median of 33 (range, 16-50) months and a decrease of the Osserman score to 0.33 +/- 0.33. In these patients MG remained stable during a follow-up period of 28 (range, 16-38) months. We conclude that long-term IA enables the reduction of oral immunosuppressants in patients with contraindications or resistance to steroid and azathioprine therapy. Furthermore, almost 50% of the patients can be weaned from IA with then substantial lower need of further immunosuppressive therapy.