We report details of renal involvement during the course of chronic graft-versus-host disease (cGVHD) in two patients undergoing bone marrow transplantation as treatment for acute leukemia. In both cases, the clinical picture was primarily characterized by proteinuria without hypertension or renal failure. Electron microscopy of renal biopsy specimens revealed a similar pattern in the two cases with extensive coalescence of foot processes and intramembraneous deposition of electron-dense material. Our data suggest that the kidney may be a target organ in chronic GVHD.