Histological and immunopathological studies were performed on serial skin biopsies from thirteen recipients of allogenic and two recipients of autologous bone marrow transplants. Marked dermoepidermal infiltration with Leu 2a+ (OKT8+) phenotype cells was found in two patients with severe graft-versus-host disease, but the infiltration did not precede clinical onset of the graft-versus-host disease. Absence of Langerhans cells was noted during the early posttransplant period in recipients of both allogenic and autologous transplantation. Intercellular epidermal staining with anti-DR was observed in three cases, without relation to graft-versus-host disease.