Nineteen adults with primary refractory or relapsed acute leukemia (12 ALL and 7 ANLL) were treated with an intensive salvage chemotherapy (intermediate-dose ara-C, intermediate-dose methotrexate, vindesine, cyclophosphamide, mitoxantrone and prednisolone) followed by a hematopoietic growth factor (HGF), either granulocyte colony-stimulating factor (5 micrograms/kg) or granulocyte-macrophage colony-stimulating factor (10 micrograms/kg). Both were given from the day after chemotherapy ended and until the neutrophil count rose above 1 X 10(9)/l for three consecutive days. Eleven patients (58%, 95% CI 33% to 82%) achieved complete remission, and 15 courses of salvage therapy were given to these complete responders. In a historical control group that did not receive HGF, 23 out of 38 patients (60%, 95% CI 44% to 77%) achieved complete remission, and 27 courses of therapy were delivered to complete responders. Treatment with a HGF accelerated the recovery of neutrophils to 0.5 X 10(9)/l significantly, shortening it from a mean of 28 to 22 days (p = .0002), with no effect on platelet recovery. There were no differences in the rates of documented and fatal infections, which were relatively high in both groups. In the patients with ANLL, there was no evidence that HGF accelerated leukemic regrowth. We conclude that HGF accelerates neutrophilic recovery following intensive salvage chemotherapy for acute leukemia, although no reduction in documented infections was found. Many factors, including the small patient sample, may have contributed to this latter finding.