Optimal delivery of chemotherapy in AIDS patients with Kaposi's sarcoma (KS) is frequently limited by hematological toxicity, mainly neutropenia. We have conducted an open-label study to investigate the safety and efficacy of recombinant human granulocyte colony-stimulating factor (filgrastim, r-metHuG-CSF) administration in 25 AIDS patients with pulmonary KS treated with Adriamycin, bleomycin, and vincristine (ABV) combination. The patients were assigned to receive r-metHuG-CSF (Neupogen, Dompé, Biotec, 5 mg/kg of body weight per day) injected subcutaneously for 3-5 days before chemotherapy until the absolute neutrophil count was higher than 25 x 10(9); r-metHuG-CSF was then discontinued 5 days before chemotherapy. Patients were eligible to resume r-metHuG-CSF 3 days after completing the anticancer regimen until normalization of the absolute neutrophil count occurred, for a maximum of 10 days. The cytotoxic regimen included vincristine 1.4 mg/m2, bleomycin 10 mg/m2, and doxorubicin 20 mg/m2, every 2 weeks. The overall response rate was 58% with a complete response rate of 18%. Median survival was 11 months and median response duration was 6 months. Adverse effects consisted of transient nausea and vomiting in 48% of patients, and moderate headache in 43%. Hematologic toxicities included anemia in 27%, and mild to moderate neutropenia (grade II-III) in 38%. The mean leukocyte and neutrophil nadirs were 1920 and 850 mm3. The mean duration of neutropenia was 3.2 days. The combination of r-metHuG-CSF and ABV chemotherapy was well tolerated. Administration of r-metHuG-CSF within 5 days before chemotherapy appears to be an acceptable treatment with important clinical implications. We stress that further studies are needed to determine the maximum tolerable doses of combination chemotherapy supported by G-CSF in AIDS-associated KS patients.