High-dose methylprednisolone (HDMP) has been shown to induce differentiation of myeloid leukemic cells with a remarkable antileukemic effect in children with various subtypes of acute myeloblastic leukemia (AML). Here the beneficial effect of short-course HDMP therapy in a child with myelodysplastic syndrome (MDS) is reported. Oral methylprednisolone sodium succinate (Prednol-L) was administered at a single daily dose of 30 mg/kg for 5 days to a 4-year-old girl with refractory anemia with excess of blasts and hypocellular bone marrow before the initiation of chemotherapy. In addition to dramatic clinical improvement, the patient's white blood cell count increased from 2.3 x 10(9)/L to 5.0 x 10(9)/L, and peripheral blood blast cells disappeared 4 days after HDMP treatment. Repeated bone marrow aspirate 1 week after the initiation of HDMP disclosed increased cellularity with no blasts. Furthermore, short-course HDMP treatment stimulated the increase in the number of peripheral blood lymphocytes and CD3+, CD4+, CD8+, CD19+, CD34+, and NK cells. Results obtained with HDMP from the previous studies and the present case suggest that high-dose methylprednisolone is a promising agent in the treatment of AIDS and it is recommended as an initial treatment especially for MDS children with hypocellular bone marrow at presentation.