Recombinant granulocyte colony-stimulating factor (r-GCSF) is used in autologous bone marrow/peripheral blood progenitor cell transplantation (ABMT/PBPC) to shorten the period of neutropenia. As these patients require platelet transfusions, their sera may be monitored for the presence of platelet/human leukocyte antigen (HLA) antibodies. Sera of some patients on r-GCSF (16