The studies questioned different target populations, including professional adults, elementary and secondary school students, and university students. Professional adults in Ontario, Canada, reported they would first go to other professionals and the media for drug information. Students in California said they would go to parents, television, and friends, while students in Ontario indicated they would ask friends, nonusers, and physicians. Young people in Ontario, Connecticut, and Kansas who used drugs said other drug users or ex-users were the most credible sources of drug information, while young people who did not use drugs identified scientists, physicians, and the media. Drug users generally trusted drug information from friends and physicians, while nonusers said they trusted the media and health professionals. Friends and the media most influenced drug use decisions. Implications of the findings for drug education programs are discussed. 16 references and 2 tables