At present, the anti-oxidant and free radical scavenging effects of plant constituents is of great research interest. Over 4,000 different types of flavonoids have been described to date. Epidemiological studies have indicated an inverse association between the intake of selected flavonoids and cancer, coronary heart disease and stroke among older adults. This lecture will review the antioxidant activity of flavonoids, which are generally more potent and effective against a broader range of oxidants than traditional anti-oxidant nutrients like vitamins C, E, beta carotenes, selenium and zinc.