Social Marketing and Diffusion-Based Strategies for Communicating with Unique Populations: HIV Prevention in San Francisco JAMES W. DEARING Department of Communication Michigan State University East Lansing, Michigan, USA EVERETT M. ROGERS Department of Communication and Journalism University of New Mexico Albuquerque, New Mexico, USA GARY MEYER Department of Communication Studies Marquette University Milwaukee, Wisconsin, USA MARY K. CASEY Department of Communication Michigan State University East Lansing, Michigan, USA NAGESH RAO Department of Communication and Journalism University of New Mexico Albuquerque, New Mexico, USA SHELLY CAMPO GEOFFREY M. HENDERSON Department of Communication Michigan State University East Lansing, Michigan, USA We conducted a 2-year investigation of the extent to which strategies based on social marketing and diffusion of innovations concepts are used in preventive health commu- nication with unique (highly ostracized) populations. Of the 49 organizations in San Francisco that operate HIV prevention programs (N = 100), programs that most highly targeted unique populations were surveyed. Personal interviews were then conducted Journal of Health Communication, Volume 1, pp. 343–363, 1996 Copyright © 1996 Taylor & Francis 1081-0730/96 $12.00 + .00 343 The present research was funded by U.S. Agency for Health Care Policy and Research Grant 5R01HS0760-02. We are indebted to our respondents in San Francisco and to our colleagues at the University of California at San Francisco for AIDS Prevention Studies, to the San Francisco Department of Public Health, and to the National AIDS Clearinghouse at the Centers for Disease Control and Prevention. Solicited as well as anonymous reviewers provided extremely valuable feed- back on earlier versions of this article. Address correspondence to Dr. James W. Dearing, Department of Communication, Michigan State University, East Lansing, MI 48824-1212, USA.