Phenolic compounds were measured in leaf tissues of apple cvs Jonagold and Golden Delicious, healthy and infected by Venturia inaequalis. Leaves were sampled from May to September 2005 and analyzed by high performance liquid chromatography. Hydroxycinnamic acids detected were chlorogenic, caffeic, ferulic and p-coumaric. In addition, the presence was ascertained of the dihydrochalcone phloridzin and the flavonoids epicatechin, catechin, rutin and quercitrin. Total phenolics were determined with the Folin-Ciocalteu method. Infection by V. inequalis caused an accumulation of phenolic compounds in infected leaves with a 1.4 to 6.2-fold increase of flavonols, a 2 to 6-fold increase of chlorogenic acid and a 1.4 to 2.4-fold increase of the Folin-Ciocalteu values.