Neither single-agent therapy nor any combination treatment has been satisfactory enough to be regarded as standard in systemic advanced Kaposi sarcoma. In an attempt to achieve high efficacy in combination with low toxicity, we used a new liposomal formulation of doxorubicin. Pharmacologic data had established a long plasma half-life, an increased accumulation in tumor tissue, and a decrease in uptake by tissues such as liver, spleen, and bone marrow. In a phase I/II open-label, dose-escalating trial 40 male AIDS patients with advanced Kaposi sarcoma were enrolled to receive intravenous “stealth” liposomal doxorubicin biweekly at doses of 10 mg/m2(n = 10), 20 mg/m2(n = 27), and 40 mg/m2(n = 3). The median CD4 count at baseline was 25/μL. After six cycles (12 weeks), 39 patients were evaluable. Three patients (7.5%) showed a complete response, which was histologically confirmed. A partial response was documented in 33 patients (85%). Stable disease was observed in three patients (7.5%). During a median treatment duration of 25 weeks, four patients developed stomatitis (10%), and four patients (10%) experienced alopecia. The most frequent hematologic toxicity was neutropenia. Grade 4 neutropenia was seen in 42.5%, and grade 3 toxicity was seen in 30%. Toxicity was dose-dependent and more frequent in the 40 mg/m2stratum. During a median observation period of 25 weeks, opportunistic infections occurred in 57.5% of the patient population. We conclude that liposomal doxorubicin at dose levels of 10 and 20 mg/m2is safe and effective for treatment of advanced Kaposi sarcoma in AIDS. A controlled trial comparing liposomal doxorubin to conventional combination therapy is underway.