Transfusion-associated graft-versus-host disease (TAGVHD) occurs in immunocompromised persons who receive nonirradiated blood products containing immunologically competent donor lymphocytes. TAGVHD occurs almost exclusively as an acute illness and has a very high mortality rate. We describe a patient with a long history of non-Hodgkin's lymphoma in whom acute TAGVHD developed after transfusion of packed red blood cells from two unrelated donors. TAGVHD developed despite pretreatment of the transfused units with white blood cell filters. The patient survived and subsequently had clinical manifestations typical of chronic cutaneous graft-versus-host disease. HLA phenotyping studies suggested that elements from both transfusion donors engrafted. TAGVHD is a rare but probably underdiagnosed disorder that, although usually fatal, may evolve into chronic graft-versus-host disease. Treatment of blood products with white blood cell filters does not appear adequate to prevent TAGVHD.