For some, the occurrence of as many as 40,000 new human immunodeficiency virus (HIV) infections in the United States each year is evidence that HIV education and prevention efforts have failed. To the contrary, more than a decade of experience with HIV has demonstrated that lasting changes in behavior needed to avoid infection can occur as a result of carefully tailored, targeted, credible, and persistent HIV risk-reduction efforts. Given experience in other health behavior change endeavors, no interventions are likely to reduce the incidence of HIV infection to zero; indeed, insisting on too high a standard for HIV risk-reduction programs may actually undermine their effectiveness. A number of social, cultural, and attitudinal barriers continue to thwart the implementation of promising HIV risk-reduction programs. The remote prospects for a successful prophylactic vaccine for HIV and the difficulty in finding effective drug treatments have underscored the importance of sustained attention to HIV prevention and education. A series of "correlates of immunity" are identified--precedents that must exist to establish effective HIV prevention programs. These include sound policies promoting HIV risk reduction; access to health and social services, condoms, needles, and syringes; interventions shown to motivate behavioral change; organizations capable of reaching those at risk; and development and diffusion of technologies to interrupt the spread of the virus.