Bone marrow (BM) histiocystosis in association with the administration of granulocyte-macrophage colony-stimulating factor (GM-CSF) is a rare phenomenon with few published cases. We report two cases of BM histiocystosis in patients with Hodgkin's disease treated with GM-CSF after autologous bone marrow transplantation. Both patients also developed clinical features of capillary leak syndrome, another rare complication of GM-CSF administration. GM-CSF-induced histiocystosis should now be considered in the differential diagnosis of delayed engraftment post-autotransplant.