Antioxidant activity of polyphenols present in wine is the subject of numerous studies mainly due to their beneficial effects on human health, but also the organoleptic characteristics of wine. In grapes and wine polyphenolic compounds are present in two main groups: flavonoids and nonflavonoids. Representatives of flavonoids are flavonols, flavanols, flavan-3-ols and anthocyanins, and of nonflavonoids are phenolic acids (hydroxybenzoic and hydroxycinnamic), stilbenes, anthocyanidins and proanthocyanidins. Polyphenolic composition of the wines primarily depends on the cultivar, the viticultural practices in the vineyard and the wine production technology. Antioxidants play crucial role in the reduction of free radicals by which the oxidation of downstream molecules is prevented. However, one of the main problems during the vinification process is wine browning, which is divided into enzymatic and non-enzymatic, and for which the phenols, especially o-diphenols are responsible. Enzymatic browning involves the hydroxylation reaction of phenols and non-enzymic browning can arise through several reactions which includes oxidation and polymerization. All these reactions affect discolouration of wine, where white wines take on unwanted brown color, while red wines become softer and less bitter. Measurement of antioxidant activity is based on inhibition of free radicals, chelation of metal ions and lipid peroxidation, and applied methods are ORAC, DPPH and ABTS.