This work studied the influence of the composition of wine on the evolution of oak compounds and on esters in red wines aged in American oak barrels. For this purpose, two of the most utilized grape varieties in wine-making, Merlot and Cabernet Sauvignon, were used. The wines made with these two varieties showed differences in pH and alcoholic degree. The extraction of furanic aldehydes, oak lactones, phenolic aldehydes and phenolic alcohols was higher in the Merlot wine, with higher alcoholic degree, than in the Cabernet Sauvignon wine, with lower pH. The difference in the concentration of these compounds in both wines was important up to 10-12 months of ageing, as afterwards most of these compounds were degraded. The evolution of fermenting esters was not affected by the composition of wine. (C) 2004 Elsevier Ltd. All rights reserved.