Aplastic anemia (AA) is more common in Asia than in Europe or the United States. This may be due in part to the high incidence of hepatitis-associated AA in Asia. The management of AA has evolved rapidly in Japan during the last decade. Advances in the treatment of AA have largely been the result of prospective collaborative studies of immunosuppressive therapy and the large registry of bone marrow transplantation data. These studies have revealed several differences in clinical outcome between Western and Eastern patients, differences that may reflect the effects of genetic background on response to treatment or development of adverse effects.