Flavonoids can bind the divalent cations frequently used to evaluate LDL antioxidant capacity in vitro. Flavonoids in cranberry juice (CBJ) may serve as antioxidants and promote cardiovascular health. This in vitro study characterizes CBJ effects on metal and non-metal based oxidation of human LDL. For cupric ion-initiated oxidation of LDL, thiobarbituric acid reactive substances (TBARS) formation and relative electrophoretic mobility (REM) were significantly inhibited by CBJ at a dilution of 1:10,000. Diene formation during LDL oxidation was evaluated by continuous measurement of absorbance at 234 nm. The time required for cupric ion-initiated LDL oxidations to reach maximum reaction velocity was significantly delayed by 1:10,000 dilutions of CBJ. Non-metal initiated LDL oxidation by 2,2'-azobis-amidinopropane was significantly inhibited by CBJ at dilutions of 1:10,000 and 1:5,000 for REM and TBARS tests, respectively. Protection of LDL from both metal and non-metal based oxidative injury confirms that the effects of CBJ are not due to flavonoid chelation of oxidants but due to a true and potent antioxidant capacity.