Sports nutrition supplements tempt athletes with promises of sleek, powerful bodies produced by pills, potions, and powders. However, many supplements are risky for athletes because an estimated 5% to 20% contain prohibited substances and unlabeled pharmaceuticals. Dietary supplements considered most at risk of containing unlabeled drugs and prohibited substances include those for sexual enhancement, weight loss, and muscle building. Sports governing bodies have banned or prohibited certain substances for athletes competing in all levels of sports; high school, college, elite, professional, and master athletes can all be tested. The banned ingredients can be in products unintentionally, due to poor hygiene in producing the supplement, or intentionally by the purposeful addition of unlabeled substances, such as anabolic steroids. Regardless of how the prohibited ingredient found its way into a dietary supplement, all sports organizations have a “strict liability” policy; that is, athletes are responsible for anything they put in their bodies, including dietary supplements. This article examines the issue of sports supplement contamination and provides athletes with resources to evaluate risky dietary supplements.