Various immunotherapeutic modalities have been used based on the autoimmune pathogenic mechanisms of myasthenia gravis (MG). Cell-mediated immunity as well as auto-antibodies may play a role in the remission and relapse of MG. We recently experienced two patients with MG who showed spontaneous remission fter inadvertent severe leukopenia. These findings suggest that the cell-mediated immune process is important in the treatment of MG, and selective suppression of leukocyte may induce remission in the patients with intractable MG.