Nearly 30 years on from the first description of AIDS, there are now over 33 million people estimated to be infected with HIV worldwide. Thanks to new drugs, people with HIV are now living longer and healthier lives. However, less than a third of people who could benefit currently get treatment, and for every 2 people put on treatment, 5 more are becoming infected. This lecture will look at the successes and failures of HIV prevention and explore the social, economic and technical challenges involved in slowing its future spread.