AIDS is still a major threat. ‘Treatment and prevention dilemmas’ shows that prevention and public health programmes are the most cost-effective way to health. HIV infection is preventable through biomedical strategies, such as ensuring safe blood and blood products by screening donors and testing donations; social interventions advising behaviour change, such as using condoms, having fewer partners, and practicing monogamy or abstinence; and—crucial to behaviour change—community mobilization and leadership. AIDS treatment developments are described along with the current state of antiretroviral therapy. Looking ahead, prevention remains the priority—while HIV infected people can live normal, productive lives, it is challenging and expensive.