We reviewed the clinical courses of 38 children with acquired aplastic anemia (AA). The patients were classified according to the severity criteria by the Japanese Ministry of Health and Welfare (JMHW) Study Group (22 severe, 15 moderate, 1 mild). Early death was observed only in severe cases. Eight of the non-severe cases progressed to severe in 0.5-125 months, and the long-term survival rate of non-severe AA did not differ from that of severe AA. The frequency of lymphocytes in the bone marrow was significantly higher, and the peripheral blood neutrophil count was lower in patients who died within a year, and these patients should be treated as very severe. These findings suggest that the JMHW Study Group criteria are useful for identifying AA patients with a poor prognosis, but even non-severe cases should be repeatedly evaluated. Sixteen of the 33 patients treated with corticosteroids and/or anabolic steroids (AS) showed hematological recovery. Bolus methylprednisolone (mPSL) therapy was effective in one of the 8 patients. Allogenic marrow transplant (BMT) was performed on 3 patients. One died from sepsis and engraftment was not achieved in the other two. Trilineage recovery was obtained in 3 of 6 patients treated with rhG-CSF and rhEPO with or without AS, and hemopoiesis has been maintained 6-12 months after discontinuation in 2 cases. In the other 3 patients, the neutrophil count showed transient increase. Therefore, the treatment for severe AA patients, who have no sibling donor for BMT, should be started with the combination therapy including these cytokines.