The flavonoids comprise a large group of polyphenolic compounds that are ubiquitous in vegetables, berries, and fruits, and they have been shown to possess antioxidative activity. The interactions between flavonoids and membranes composed of dipalmitoylphosphatidylcholine (DPPC) have been studied by means of noncovalent immobilized artificial membrane (IAM) chromatography. We have also investigated flavonoid-induced calcein release from fluid egg phosphatidylcholine (EPC) vesicles. Flavonoids with more hydroxyl groups showed longer retention delays in the IAM studies, suggesting stronger interactions between the flavonoids, which are rich in hydroxyl groups, and the DPPC membrane interface. We also observed an inverse correlation between the number of hydroxyl groups in the flavonoids and their capacity to induce calcein leakage through fluid EPC bilayer membranes (the more nonpolar flavonoids caused more calcein leakage). Rhamnetin and morin, however, both showed marked activity for the DPPC membrane interface and caused significant membrane leakage. Both polar and nonpolar forces were shown to have a significant impact on the flavonoid/biomembrane interactions.