Epidemiological studies have associated low dietary and/or plasma level of carotenoids with higher incidences of certain cancers. This evidence has led the National Cancer Institute to initiate more than a dozen prospective clinical trials in which supplements of beta-carotene alone, or in combination with other micronutrients, are being taken. In these trials, the beta-carotene supplements are given in the range of 15-50 mg/day. The safety of this level of intake is well documented. beta-Carotene has been successfully used to treat inherited photosensitivity diseases for more than 15 years at dosages of 180 mg/day or more, without any adverse effects other than hypercarotenemia. Toxicity studies in animals have shown that beta-carotene is not carcinogenic, mutagenic, embryotoxic, or teratogenic and does not cause hypervitaminosis A. In the few isolated reports of carotenoid-related toxicity, the findings are associated with very large intakes of foods containing beta-carotene, among other constituents, and have not been substantiated in individuals who have taken high doses of beta-carotene for several years.