Dr. Stephen Moses is a physician and scientist who has made major contributions internationally to understanding biological and behavioural risk factors for sexually transmitted infections (STIs), particularly HIV infection, and translating research findings into practice. Over the past 25 years, he has been at the forefront of investigating, and integrating into programs, three major innovations for HIV prevention: improved management and control of other “conventional” STIs; implementation of targeted, peer-led educational interventions for high-risk populations; and male circumcision for reducing HIV susceptibility among men. These initiatives have had far-ranging impact in improving the health and well-being of vulnerable populations globally.