Technical Abstract: Since the early 1990's, grapefruit juice has been implicated in drug interaction. There are indications that furanocoumarins induce the catabolism of cytochrome P450, CYP3A4 enzyme in the intestine enterocytes. This enzyme is responsible for metabolizing variable proportions of several drugs taken orally, and it’s removal has been shown to increase the bioavailability of the affected medications. Although furanocoumarins are present in various fruits and vegetables, it is their presence in grapefruit that has attracted the most attention. Studies have shown that furanocoumarins in grapefruit juice can vary significantly and from multiple causes. Most of all, furanocoumarins are stress-induced molecules, their levels affected by many factors ranging from UV exposure to insect infestation. There are also varietal and seasonal factors. In this study juice processing and storage parameters were investigated. Prolonged fruit storage prior to processing and most steps involved in juice processing had little influence on the levels of 6’,7’-dihydroxybergamottin, paradisin C, bergamottin, or bergaptol. However, products that are hot filled and storage of shelf stable or grapefruit juice products stored at room temperature will have lower amounts of 6’,7’-dihydroxybergamottin and paradisin C and higher amounts of bergaptol in the juice compared to juices which are not hot filled and stored at refrigerated temperatures. Both 6',7'-dihydroxybergamottin and paradisin C, which are potent CYP3A4 inhibitors, are replaced by bergaptol, a very weak inhibitor.Bergamottin amounts also decreased to a lesser extent. Therefore, a grapefruit juice stored at room temperature for extended periods of time will have a reduced drug interaction potential.