OBJECTIVE To define the maximum tolerated dose of doxorubicin when combined with fixed doses of bleomycin, vincristine, zidovudine, and recombinant human granulocyte macrophage colony-stimulating factor (rhGM-CSF) in patients with advanced AIDS-related Kaposi's sarcoma. METHODS Twenty male patients were treated with zidovudine at doses of either 100 or 200 mg by mouth every 4 hours, and cytotoxic chemotherapy with bleomycin 10 U/m2 and vincristine 1.4 mg/m2 by vein every 2 weeks. Four successive cohorts received fixed doses of doxorubicin given intravenously every 2 weeks: two cohorts each received 10 mg/m2 (levels 1, 2) or 20 mg/m2 (levels 3, 4). The first cohort received rhGM-CSF at a dose of 10 micrograms/ kg, given subcutaneously on days 2 through 11 (level 1). Due to toxicity, the dose of rhGM-CSF was reduced to 5 micrograms/kg (levels 2, 3) and then to 2.5 micrograms/kg (level 4). RESULTS The dose-limiting toxicity was severe neutropenia, occurring in 10 patients. Severe neutropenic episodes occurred after a median of three cycles of chemotherapy, with the nadir occurring after 14 days (median). Moderate neutropenia occurred in 14% of all cycles administered. Constitutional toxicities of moderate or greater severity occurred in four patients. Five of 10 patients at a doxorubicin dose of 20 mg/m2 (levels 3 and 4) experienced severe neutropenia. Thus, doxorubicin at 10 mg/m2, with BV (bleomycin, vincristine chemotherapy), zidovudine (100 mg five times daily), and rhGM-CSF (5 micrograms/kg/day), was defined as the maximum tolerated dose. CONCLUSIONS The maximum tolerated dose of doxorubicin is 10 mg/ m2 every 2 weeks when given in combination with BV chemotherapy, zidovudine, and rhGM-CSF. While the addition of rhGM-CSF at doses of 2.5 to 5 micrograms/kg decreased the duration of neutropenia, it did not prevent the occurrence of severe neutropenia from combined myelotoxic therapy.