The African Comprehensive HIV/AIDS Partnerships (ACHAP) played a major role in initiating Botswana's antiretroviral (ARV) program in 2001. ACHAP is a prominent public-private partnership involving Merck and its foundation, the Bill and Melinda Gates Foundation, and the government of Botswana. This paper analyses ACHAP's efforts to assist Botswana with its ARV program, the first and most advanced in sub-Saharan Africa. It identifies five features of the model and shows how they contributed to the ARV program. It also raises questions about ACHAP's role in scaling up and sustaining the program, as Botswana faces the challenges of treating growing numbers of HIV-infected people.