HIV transmission remains a threat in Canada and around the world. Men who have sex with men account for 41 percent of all new cases of HIV in Canada, and continue to be the largest proportion of new cases. However, recent trends suggest nearly 30 percent of new HIV cases occur among heterosexuals following sexual contact. Although new HIV drugs have brought hope to patients, they have also lessened the perception of HIV risk. In fact, new cases of HIV infection increased 17 percent in 2002, compared to 2000. Eli Puterman is developing a new model to predict and understand safe sex practices in two at-risk groups: heterosexuals with multiple partners, and men who have sex with men. While present HIV prevention models can predict the intention to use condoms, they are less successful at predicting whether condom use will actually occur, because they do not consider the uniqueness of each sexual encounter. Instead, Eli is investigating how individuals appraise and respond to HIV risk in different sexual situations over time. This research could provide a new model for HIV prevention strategies both within Canada and other developed countries.