To assess the prevalence of use of anabolic-androgenic steroids and other presumed performance-enhancing drugs and the associated knowledge, attitudes, and behavior of school-aged Canadians.A national survey was conducted using a self-report questionnaire distributed randomly to schools within each of five Canadian regions.Canada.The subjects were 16,119 Canadian students, in the sixth grade and above, from 107 schools drawn randomly from five Canadian regions.The number of students reporting the use of anabolic-androgenic steroids and other performance-enhancing drugs in the year before the survey, the nature of such drug-taking activities, and the atitudes underlying the decision to take anabolic-androgenic steroids.More than 83,000 young Canadians (2.8% of the respondents) are estimated to have used anabolic-androgenic steroids in the year before the survey. Of those taking such drugs, 29.4% reported that they injected them; of the latter group, 29.2% reported sharing needles in the course of injecting anabolic-androgenic steroids. Significant numbers of respondents reported using other substances (caffeine, 27%; extra protein, 27%; alcohol, 8.6%; painkillers, 9%; stimulants, 3.1%; “doping methods,” 2.3%; β-blockers, 1%) in attempts to improve sport performance.The use of anabolic-androgenic steroids is more widespread than may have been assumed and is often accompanied by high-risk needle-sharing. Anabolic-androgenic steroid use is often intended to alter body build as opposed to accentuating sport performance. Many young Canadians use a variety of other substances in attempts to improve sport performance. Drug-taking of this kind represents a special challenge for educators, health professionals, and sport authorities.