A 1-year-old boy with acute myeloid leukemia with cytomegalovirus (CMV) retinitis that was refractory because of severely impaired cellular immunity underwent bone marrow transplantation from an HLA-matched donor after a conditioning regimen of busulfan, cyclophosphamide, and etoposide. Although we continued administration of ganciclovir from preparation therapy, retinitis worsened after engraftment. Thereafter retinitis improved gradually as the number of CD4+ T-lymphocytes increased.The findings in this case suggest that stem cell transplantation for a leukemia patient with CMV disease may be effective.