An equilibrium search model of the Malawian HIV/AIDS epidemic is presented. Individuals engage in di¤erent types of sexual activity, which vary in their riskiness. When choosing a sexual activity, such as short-term sex without a condom, a person rationally considers its risk. A simulated version of the model is parameterized to match some salient facts about the Malawian epidemic. Some topical policies (e.g., male circumcision, treatment of other STDs, and promoting marriage) are studied and found to have potential to back re: Moderate interventions may actually increase the prevalence of HIV/AIDS, due to shifts in human behavior and equilibrium e¤ects.