HIV prevention in developed countries is marked by impressive successes and dismal failures. The successes point the way to what works; the failures highlight obstacles that must be overcome. Successes include important behavioural changes among gay and bisexual men, antiviral use to prevent vertical transmission, and securing the safety of the blood supply. New strategies are needed to reach the residual of individuals continuing with unsafe practices (a special hazard in high-prevalence areas); to reach young people who are beginning to engage in sexual relations and injection drug use; and to overcome political opposition to prevention strategies.