Lycopene is a carotenoid found in grapefruit, watermelons, and papaya in addition to tomatoes. It is obtained only through diet. Lycopene exhibits antioxidant and anticancer properties. Results from several epidemiologic studies suggest a strong association between high intake of lycopene-rich foods and reduced risk of several cancers, notably prostate cancer. However, few well designed clinical trials have been conducted, and data remain inconclusive. Because lycopene supplementation is associated with strong antioxidant effects, it has the potential to interfere with chemotherapy and radiation therapy. Cancer patients should use caution if considering an increase in their lycopene intake.