Copigmentation is a very important contributor to colour in young red wines. Further understanding ofthe copigmentation effect has been elucidated by investigating the contribution of various fractions ofgrapes ' skin, pulp, and seed ' in varieties Shiraz, Sangiovese and Pinot Noir. A series of spectrophotometricand HPLC experiments elucidated the effect of this interaction in grape extracts simulating wine conditions.A post-column reaction method was developed to permit the evaluation of the reactivity of eachgrape anthocyanin with different reagents: pure compounds (quercetin and caffeic acid) and extracts ofgrape sections (seed, Semillon skin, Semillon pulp). Certain extracts produced a decrease in colour, suggestingthat competing equilibria are important in the copigmentation effect and that an ''anti-copigmentation''effect is possible. Flavonols appear to be the best copigmentation cofactors, and the concentrationof quercetin 3-O-glucoside was found to correlate with the strength of copigmentation. Flavonols appearcapable of displacing cofactors derived from seed extracts.