The authors of this article provide an overview of a PLoS collection of mathematical modeling studies on voluntary medical male circumcision (VMMC). These models are helping countries examine the potential effects on program impact and cost-effectiveness of prioritizing specific subpopulations for VMMC services by, for example, client age, HIV-positive status, risk group, and geographical location. The modeling also examines long-term sustainability strategies, such as adolescent or early infant male circumcision, to preserve VMMC coverage gains achieved during rapid scale-up.