Technical Abstract: This paper reviews the theoretical and the epidemiologic evidence that beta-carotene may play a role in prevention of chronic diseases: specifically cardiovascular disease and cancer. Beta-carotene could act to prevent cardiovascular disease by preventing oxidation of cir- culating particles known as low density lipoproteins. Once oxidized, low density lipoproteins are thought to be toxic to blood vessels. Beta-carotene could work to prevent cancer by acting as a vitamin A precursor or preventing free radical damage to the gene. To date, the evidence is strongest that beta-carotene may be protective against lung cancer and cancers of the upper gastrointestinal tract (esophagus, stomach). Several long-term intervention trials will be needed to determine if a single nutrient (such as beta-carotene) can act alone to reduce the risk of cancer at these sites.