The use of herbs for medical benefit has played an important role in nearly every culture on earth. Herbal medicine was practiced by ancient cultures in Asia, Africa, Europe and the Americas. The recent popularity in use of herbals can be tied to the belief that herbs can provide some benefit over and above allopathic medicine and allow users to feel that they have some control in their choice of medications. The widespread use of herbs, either directly or as dietary supplements, has raised many scientific questions. Are herbal preparations safe? Do herbs interact with pharmaceutical medications to enhance or reduce their efficacy? The first interaction can be shown by the effects of St. John's Wort, a mild herbal antidepressant, and many commonly used medicines. St. John's Wort can induce the CYP3A family of activation enzymes through which approximately 50% of drugs are metabolized. This poses some risk of inadvertently reducing the half-life of such drugs as indinavir, cyclosporin and cyclophosphamide. On the other hand, herbal products may act in a pathway similar to pharmaceuticals yet without side effects. Natural anti-inflammatory compounds abound in the herbal world and are found in green tea, the spices turmeric and rosemary, feverfew and others. Because the use of nonsteroidal anti-inflammatory drugs (NSAID) is associated with a reduced risk for several cancers, it is at least plausible that natural NSAID should be explored for possible use as cancer preventives.