The introduction in the mid-1990s of highly active antiretroviral therapy (HAART) helped HIV become a manageable disease in industrialized settings such as Canada. Mortality and morbidity associated with HIV have been dramatically reduced with the increased use of these drug regimens and are associated with reduced transmission probability of HIV within sexual relationships. It has been proposed that HAART be integrated into HIV-prevention activities as a means of helping curb epidemic growth. Evaluating the impact of HAART is complex. For example, while the effect of reduced symptoms and increased lifespan is beneficial to the individual, modelling studies have shown that unless infectiousness of individuals is sufficiently reduced by antiretrovirals, the negative impact of an increased incubation period (leading to increased number of opportunities for transmitting infection and a larger population of transmitters) can actually increase how fast the infection spreads. Using mathemathical modelling methods, Kathleen Deering is comparing the impacts of HAART in Vancouver (where HIV-infected individuals have free access to treatment), and in southwest India (where only about 10 per cent of HIV-infected people have access). Her studies, which consider infection biology, behavioural and demographic characteristics of the population, and the spread of infection over time, will be used to compare different treatment strategies for HAART, and to project disease outcomes. Deering’s research will provide evidence for developing HIV treatment and care recommendations that will help maximize the effectiveness of HAART among marginalized groups in Canada and India.