G-CSF is routinely administered after autologous bone marrow or peripheral blood progenitor cell transplantation to enhance neutrophil engraftment. However, many different doses of G-CSF have been described with no clear consensus on the most cost-effective dose. We performed a prospective randomized trial examining the efficacy of three different doses of G-CSF post-autologous transplant (5, 10, or 16 micrograms/kg/day). Fifty-seven consecutive patients with breast cancer (n = 30), non-Hodgkin's lymphoma (n = 16), Hodgkin's disease (n = 6), multiple myeloma (n = 2), acute leukemia (n = 2), and testicular cancer (n = 1) were randomized, with 19 patients enrolled in each of the three treatment groups. All patients underwent a high-dose chemotherapy preparative regimen and received an autologous peripheral blood progenitor cell (PBPC) transplant (without bone marrow), with G-CSF beginning on day 0. There was no difference in time to neutrophil engraftment among the three treatment groups (mean 10.2 to 10.8 days). There is a trend towards earlier platelet engraftment in the patient group receiving 5 microgram/kg/day of G-CSF. The total cost of G-CSF by dose group was $2900, $4400, and $6500 per patient. We conclude that there was no advantage to the use of higher doses of G-CSF after autologous transplantation, and that lower doses are associated with lower costs.