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. Naringin 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 bergomattin, and flavonoids, such as naringin, may play the most active roles in the effects of grapefruit on plasma drug levels. In light of its popularity, grapefruit has been associated with increased bioavailability of many drugs.