BACKGROUND: Visceral leishmaniasis (VL) in human immunodeficiency virus (HIV) co-infected patients requires special case management. AmBisome monotherapy at 40 mg/kg is recommended by the World Health Organization. The objective of the study was to assess if a combination of a lower dose of AmBisome with miltefosine would show acceptable efficacy at the end of treatment. METHODOLOGY/PRINCIPAL FINDINGS: An open-label, non-comparative randomized trial of AmBisome (30 mg/kg) with miltefosine (100 mg/day for 28 days), and AmBisome monotherapy (40 mg/kg) was conducted in Ethiopian VL patients co-infected with HIV (NCT02011958). A sequential design was used with a triangular continuation region. The primary outcome was parasite clearance at day 29, after the first round of treatment. Patients with clinical improvement but without parasite clearance at day 29 received a second round of the allocated treatment. Efficacy was evaluated again at day 58, after completion of treatment. Recruitment was stopped after inclusion of 19 and 39 patients in monotherapy and combination arms respectively, as per pre-specified stopping rules. At D29, intention-to-treat efficacy in the AmBisome arm was 70% (95% CI 45-87%) in the unadjusted analysis, and 50% (95% CI 27-73%) in the adjusted analysis, while in the combination arm, it was 81% (95% CI 67-90%) and 67% (95% CI 48-82%) respectively. At D58, the adjusted efficacy was 55% (95% CI 32-78%) in the monotherapy arm, and 88% (95% CI 79-98%) in the combination arm. No major safety concerns related to the study medication were identified. Ten SAEs were observed within the treatment period, and 4 deaths unrelated to the study medication. CONCLUSIONS/SIGNIFICANCE: The extended treatment strategy with the combination regimen showed the highest documented efficacy in HIV-VL patients; these results support a recommendation of this regimen as first-line treatment strategy for HIV-VL patients in eastern Africa. TRIAL REGISTRATION NUMBER: www.clinicaltrials.gov NCT02011958.