Some psychoactive drugs have actual performance-enhancing side effects. However, many actually decrease performance, primarily because of adverse cardiovascular effects and impaired judgment. Athletes and nonathletes alike may be knowingly or unknowingly exposed to psychoactive substances if they use over-the-counter, recreational, or prescription drugs. Many national and international sports federations ban or limit psychoactive drug use. The physiologic actions of psychoactive drugs and their use by high school and college athletes are discussed here.