Drug testing at work is rapidly becoming the standard in the United States. For drug testing to fulfill its promise as a vital part of the effort to end the drug abuse epidemic, it is essential that the tests be reliable so that people who are not using drugs are not falsely accused and that legitimate medical use of controlled substances not expose employees to harassment or labeling as drug abusers. To merit employee confidence, workplace drug testing needs to be made part of a program that includes these basic elements: (1) a clear and comprehensive policy; (2) secure collection; (3) chain-of-custody procedures; (4) retained positive samples; (5) an initial screening test; (6) a sophisticated confirmatory test; (7) a medical review officer; (8) a retest of retained positive samples in disputed cases; and (9) a system of quality control. In addition, this drug testing program needs to be built on a solid foundation that distinguishes between legitimate use of prescribed medicines and nonmedical drug use. This differentiation is the primary responsibility of the medical review officer.