The authors review the major scientific milestones and the legislative framework that have made possible the spectacular successes of many modern therapies that trace their origins to plants. They emphasize that drugs used in mainstream medicine, in contrast to most of those used in alternative medicine, are required to meet stringent federal requirements for purity, safety, and efficacy before they can be distributed to the public, and that the necessary testing requires much time and effort. Yet alternative medicines based on plant substances are extremely popular, even though their safety and efficacy have not been scientifically proven. Reasons for this are reviewed and numerous examples and case histories are cited illustrating both successes in the scientific development of drugs from plants and the dangers of unregulated drugs. Such drugs are more easily available because of the deregulating effect of the 1994 Dietary Supplement Health and Education Act (DSHEA), which has substantially weakened the authority of the Food and Drug Administration to ensure the safety of dietary supplements. The authors describe the rigorous scientific investigations of curcumin, from the ginger family, and of sulforaphane, from crucifers, to illustrate the long and demanding scientific process that is required to establish the safety and effectiveness of potential drugs from plants. They re-emphasize the necessity for strict scientific review of all drugs. They also recommend that all providers of care be required to question patients about their intakes of dietary supplements. The authors close by saying that the DSHEA is "a disaster waiting to happen," but warn that any attempts to strengthen current legislation will be opposed by special interests.