Abdominal complications were evaluated with ultrasonography in 20 patients who received marrow-ablative chemotherapy and bone marrow or blood stem cell transplantation for the treatment of hematologic malignancies. Ultrasonographic findings compatible with veno-occlusive disease of the liver, cytomegalovirus infection of the colon, hepatic lesion of graft-versus-host disease, and cyclophosphamide-induced hemorrhagic cystitis were demonstrated in 6 of these patients. In addition, ascites, pleural effusion, gall bladder wall thickening, and hepatosplenomegaly were easily detected. Since ultrasonography is noninvasive and can be repeated, ultrasonographic studies are useful for evaluating and monitoring abdominal complications which are frequently encountered in these transplant patients.