Two patients with poor prognosis stage III multiple myeloma have been treated with myeloablative chemoradiotherapy, i.e. 10 Gy fractionated total body irradiation plus 120 mg/m2 intravenous melphalan, and then transplanted with autologous peripheral blood cells harvested by four leukaphereses during the phase of rapid hematopoietic recovery following induction therapy with high-dose (2 g/m2) etoposide and recombinant human glycosylated granulocyte macrophage-colony stimulating factor (rhGM-CSF). Following myeloablative therapy and autologous peripheral blood cell transplantation, both patients experienced brief pancytopenia followed by rapid hematopoietic recovery of leukocytes (time to greater than 500 x 10(6)/l = 12 days) and platelets (time to greater than 100 x 10(9)/l = 14 days). In particular, single donor platelet transfusion requirements were limited to one and two transfusions per patient, respectively. Reconstitution has so far been maintained throughout the follow-up period for the two patients (9 and 6 months, respectively). These two cases show that rhGM-CSF-exposed peripheral blood cells are capable of producing prompt and sustained hematopoietic reconstitution in patients treated with myeloablative chemoradiotherapy.