The use of alcohol, tobacco, and other drugs—whether legal or illegal—by various age groups and special populations continues to be a problem in the United States. The use of illegal drugs increased among American adolescents throughout the 1990s, and this increase caused special concern. In response, the American public has become increasingly interested in the concept of prevention. The prevention movement began in the 1970s and has gained in popularity since then. Parents have organized to address the factors that lead to substance abuse, in order to prevent drug use among young people. In many cases, youth groups have also formed to help parents prevent sub- stance abuse among young people and their peers. Supporters of the prevention movement emphasize that preventing substance abuse has a greater chance of success than helping people quit after they have become addicted. They also point out that prevention is...