Grapefruit is a popular dietary component among North Americans. The active chemical compounds in grapefruit include flavones, isoflavones, flavonols, furanocoumarins and anthocyanidin, which have been found to have antioxidant, anti-inflammatory and antimi- crobial activities. The flavonoids of interest include naringin, quercetin and kaempferol. Nar- ingin composes about 10% of the dry weight of grapefruit, and is responsible for its taste and odor. It is hydrolyzed to naringenin by intestinal flora. Furanocoumarins, such as bergomat- tin, and flavonoids, such as naringin, may play the most active roles in the effects of grape- fruit on plasma drug levels. In light of its popularity, grapefruit has been associated with increased bioavailability of many drugs.