Several presentations at the 2007 Conference on Retroviruses and Opportunistic Infections focused on the underlying factors driving the HIV epidemic in selected regions of the world and on selected populations. The conference also provided updated data on 1 of 2 successful adult male circumcision efficacy trials to prevent HIV acquisition, and a review of 1 of 2 unsuccessful efficacy trials of the microbicide cellulose sulfate. Presentations also focused on strategies to prevent HIV acquisition through pre-exposure prophylaxis, treatment of sexually transmitted diseases, and prevention of mother-to-child transmission through breastfeeding.