In patients with hematologic malignancies, granulocyte colony-stimulating factor (G-CSF) following chemotherapy is widely used to mobilize peripheral blood progenitor cells (PBPCs), but there have been no trials comparing schedules of G-CSF following chemotherapy. We conducted a prospective randomized comparative observation of the mobilization with a single dose (10 microg kg once a day) or split dose (5 microg kg twice a day) of lenograstim following chemotherapy in 25 multiple myeloma (MM) and 15 non-Hodgkin's lymphoma (NHL) patients. Chemotherapy was cyclophosphamide 4 g/m2 for MM and ESHAP with or without Rituximab for NHL. The median number of harvested CD34+ cells was 19.4 x 10(6)/kg and 15.8 x 10(6)/kg in the single- and split-dose groups, respectively (p=0.47). Targeted collection of 5 x 10(6) CD34+ cells/kg was achieved in 18/20 patients in the single-dose group and in all 20 patients of the split-dose group (p=0.24), with the median number of sessions 1 and 2 in the single- and split-dose groups, respectively (p=0.13). We could not observe statistically significant differences between a single-dose and split-dose lenograstim following chemotherapy in enhancing the mobilization of PBPCs in MM or NHL patients.