Polyphenols are among the most ubiquitous groups of molecules distributed in food of plant origin. There is a variety of biological effects exerted by polyphenols in vitro and in vivo including antioxidant, antimutagen and anti-inflammacory effects. To evaluate a potential beneficial effects of polyphenols in human health, it is necessary to understand absorption, distribuition and metabolism of these compounds. The main structural parametars that effect intestinal absorption of polyphenols are molecular weight, glycosilation and esterification. Most polyphenols with exception of catechins and proantocyanidins are rarely found in free form in food. Flavonoids occur mainly glycosilated and phenolic acids esterified to small organic acids or arabinoxylans from plant cell walls. They are partly hydrolised to their aglycones in small intestine and extensively by enzymes of bacterial origin in colon. Their pharmacological effects are highly dependent on the number and position of the hydroxyl groups in the molecule. These groups are mainly conjugated to form O-glucuronides, sulphate esters and O-metyl ethers. Thus conjugation of polyphenols effects their biological and toxical properties and consequently the health itself. Polyphenols are almost entirely conjugated and unmodified forms are generally either absent or present in low concentrations. Oxidation is less represented methabolic pathway, but can also have significant influence on biological properties. Given metabolic reactions occur mainly in liver and small intestine. Conjugates effluxed back from enterocytes to intestinal lumen or excreted from liver through the bile, reach the colon where they are hydrolised by microbial enzymes into aglycones and reabsorped, resulting in enterohepatic cycling. Colon microflora also metabolise non absorbed polyphenols in a wide array oflow molecular weight compounds. These metabolites are responsabile for some of the health effects of polyphenols, parti-· culary of those poorly absorbed through the small intestine.