The case studies of the diffusion of the two AIDS/HIV prevention programs indicate that there are at least three different models of the relationship between the effectiveness of a public health program and its diffusion: (1) diffusion on the basis of firm evidence of effectiveness; (2) widespread diffusion without evidence of effectiveness; and (3) lack of diffusion despite evidence of effectiveness. The authors provide overviews of both the D.A.R.E. program and syringe exchange programs before discussing their diffusion across the United States and internationally. D.A.R.E. has spread widely since its development in 1983. It is currently used in 80 percent of United States school districts and in 54 other countries. Syringe exchange programs, which began in Amsterdam in 1984, expanded into other Dutch cities, the United Kingdom, and Australia by 1987 and into almost every industrialized nation by the mid-1990s. Sweden and the United States remain the only industrialized nations not to have a national syringe exchange program. The authors analyze these patterns of diffusion for D.A.R.E. and syringe exchange programs through a review of each program’s effectiveness. According to research data, the D.A.R.E. program is not effective at reducing drug use among youth. Syringe exchange programs, on the other hand, have been shown to be effective at reducing AIDS/HIV among injection drug users and to not cause an increase in injection drug use. In order to understand why D.A.R.E. was widely diffused while syringe exchange was not, the authors apply the concepts of framing and loss aversion decisionmaking. Framing refers to the process by which decisionmaking must fit within existing values and past experiences. Loss aversion refers to a decisionmaking process in which the avoidance of certain losses, such as the loss of the entire zero tolerance framework, is more important than opportunities for gain. References