Intravenous (IV) granulocyte colony stimulating factor (G-CSF) might be safer and more convenient than subcutaneous (SC) administration to hospitalized hemato-oncological patients receiving chemotherapy. To compare IV vs. SC G-CSF administration, we conducted a randomized, open-label trial. We included inpatients receiving chemotherapy for acute myeloid leukemia, acute lymphoblastic leukemia, lymphoma or multiple myeloma, and allogeneic or autologous hematopoietic cell transplantation (HCT). Patients were randomized to 5 mcg/kg single daily dose of IV bolus versus SC filgrastim given for its clinical indications. Patients were crossed-over to the alternate study arm on the subsequent chemotherapy course. The primary outcomes were time from initiation of filgrastim to recovery of stable neutrophil count of >500 cells/μL and a composite clinical outcome of infection or death assessed for the first course post-randomization. The study was stopped on the second interim analysis. Of 120 patients randomized, 118 were evaluated in the first treatment course. The mean time to neutropenia resolution was longer with IV G-CSF [7.9 days, 95% confidence interval (CI) 6.6-9.1] compared with SC G-CSF (5.4 days, 95% CI 4.6-6.2), log-rank P=0.001. Longer neutropenia duration was observed in all patient subgroups, except for patients undergoing autologous HCT. There was no significant difference between groups in the occurrence of infection or death, but more deaths were observed with IV (4/57, 7%) versus SC (1/61, 1.6%) G-CSF administration, P=0.196. Similar results were observed when all 158 courses following cross-over were analyzed. Patients reported similar pain and satisfaction scores in both groups. Bolus IV administration of G-CSF results in longer neutropenia duration than SC administration, with no difference in clinical or quality-of-life measures.