Transmission of drug resistance in the context of HIV-1 treatment is an important threat for the efficient control of the HIV-1 pandemic. The recent initiation of antiretroviral therapy (ARV) programs in Africa highlights the importance of studying this problem in more depth. In a recent issue of Science (Smith, et al. Science. 2010;327:697-701) a mathematical analysis was presented of the transmission of HIV-1 drug-resistant strains in the San Francisco community of men who have sex with men (MSM). The model is able to track the accumulation of resistance against multiple drug classes. By setting parameters for the model with detailed data on the San Francisco’s MSM community, the authors tried to understand and predict the evolutionary dynamics of wild-type and multiple ARV-resistant strains in this population. The initial conditions of the model were calibrated to match the epidemiological conditions in San Francisco in 1987 when zidovudine (AZT) was introduced. Then, the model was used to simulate the evolutionary history of ARV resistance in San Francisco and to predict its future dynamics.