Four weeks following autologous bone marrow transplantation for Wilms' tumor, a patient developed fever, hepatomegaly, coagulation disorders and pancytopenia. Bone marrow studies showed progressively increased hemophagocytosis of normal hematopoietic progenitors by histiocytes resulting in aplasia. Adenovirus type 11 was consistently isolated from urine and stool cultures, and one of the marrow aspirates. At autopsy, adenovirus was isolated from the lungs, liver, heart, intestine and spleen. These findings are consistent with the previously described virus-associated hemophagocytic syndrome, which have not been associated with bone marrow transplantation. This case suggests that this diagnosis should be considered in any bone marrow transplant patient who has evidence of secondary graft failure.