The aplastic anemia methimazole induced is a rare event. We describe a case of a woman, affected by hyperthyroidism, who suffers from bone marrow aplasia during Tapazole treatment, and literature has been reviewed. Stopping methimazole and beginning a therapy with methylprednisolone in high dosage, intravenous IgG in high dosage, filgastrin and danatrol, medullary recover after 11 days of treatment is obtained. By analyzing our case and the 12 further cases described, we find that the prognosis of aplastic anemia during the treatment of antithyroid therapy, is rather good. Even if the pathogenetic mechanism of Tapazole induced bone marrow aplasia, it seems to be immuno-mediated in most cases, a direct toxicity in bone marrow cannot be excluded. In examined cases the antithyroid dosage was medium high (mean 40 mg/die). Therefore the use of Tapazole in low doses (15 mg/die) effective in almost all hyperthyroid patient must be considered, when possible, the best therapeutic choice, since it is safer in the incidence of important side effects such as bone marrow aplasia, especially in elderly patients or in patients with chronic renal failure.