This statement summarizes the U.S. Preventive Services Task Force (USPSTF) recommendations on routine vitamin supplementation to prevent cancer and cardiovascular disease and the supporting scientific evidence. Part of the information on which this statement is based, including evidence tables and references, is available in the accompanying article on vitamins to prevent cardiovascular disease in this issue. More complete information can be found in the summaries of the evidence on vitamins to prevent cancer and vitamins to prevent cardiovascular disease, available on the USPSTF Web site (http://www.preventiveservices.ahrq.gov) and through the National Guideline Clearinghouse (http://www.guideline.gov). The summaries of the evidence on these topics and the recommendation statement are also available in print through subscription to the Guide to Clinical Preventive Services, Third Edition: Periodic Updates. A subscription costs $60 U.S. and can be ordered through the Agency for Healthcare Research and Quality Publications Clearinghouse (call 800-358-9295 or e-mail mailto:firstname.lastname@example.org).