Flavonoids are a large group of naturally occurring polyphenolic compounds which are ubiquitous throughout the plant kingdom and are bio-available in fruits, vegetables, nuts, seeds, flowers, and bark. Quercetin has raised particular interest as it is not only a major component of the naturally occurring dietary flavonols, but it also seems to have anti-oxidant, anti-carcinogenic, anti-inflammatory, as well as cardioprotective functions. Recently, our laboratory and others have reported that quercetin, in addition to its other functions, plays a role in improving the function of chloride (Cl-) transport in the (CFTR).