In the second half of the twentieth century, political scientists observed a remarkable increase in policy convergence across disparate issue areas. The literature on policy diffusion suggests that countries are likely to converge around internationally accepted norms of behavior. These include, for example, public health policies designed to deal with epidemics such as polio, tuberculosis, SARS, and HIV/AIDS. Most countries treat these epidemics in similar and in some cases almost identical ways. States where epidemics emerge relatively late are at an extraordinary advantage. They not only have the expertise of a number of international organizations and their technical assistance at their disposal, but also the experience of other states. Once successful policies to address such epidemics are identified, many states choose to adopt these approaches. However, when it comes to the prevention of HIV/AIDS, Russia's policy is an outlier. While the Russian Federation is facing the fastest growing HIV/AIDS epidemic in Eastern Europe, it remains one of the few states that refuses to implement key interventions. The goal of this dissertation is to examine why this is the case. I investigate the role of domestic factors in shaping HIV/AIDS policies in Russia. Existing literature suggests that the political regime, the development of civil society, and patterns of federalism are some of the factors that might explain variation in state responses to the HIV/AIDS epidemic. In contrast, I demonstrate that path-dependent factors, such as the influence of the medical epistemic community and the politics of morality, account for the absence of HIV/AIDS policy diffusion in Russia. I argue that in the Russian Federation, HIV/AIDS prevention policies are undermined due to lack of state will and centralized authority. Therefore, individual agencies conduct interventions without a specific mandate to prioritize a response to the HIV/AIDS epidemic. These agencies design and implement interventions in accordance with their established priorities, norms, and practices, which are strongly path-dependent. In particular, I show that institutionalized influence of the domestic medical epistemic community and the politics of morality on policy-making processes prevent the adoption of best practices in Russia's response to the HIV/AIDS epidemic.