Abstract:  Tea is a pleasant, popular and safe beverage. Tea provides a dietary source of bioactive components to help humans reduce a wide variety of cancer risks and chronic diseases. The antioxidative activity of green tea- derived polyphenols known as catchins has been extensively studied. The reductive effect is a synergistic action between EGCG, EGC, ECG, EC, pheophytins a and b, and other components in tea leaves, which are more bioavailable for human body. Green tea has a higher content of catechins than black tea. Green tea extract with hot water has high potential and more efficiency to reduce cancer risk than any other tea products or pure EGCG. Protein, iron, and other food components may interfere with the bioavailability of tea polyphenols. Drinking green tea (or polyphenol- rich tea extract) also enhances the cancer- preventive activity of some cancer- fighting medication such as Sulindac and Tamoxifen. Further studies are required to determine the bioavailability of green tea and cancer- preventive functionality.