1H NMR and targeted HPLCs were used to analyse the response of peach (Prunus persica L. Batsch) to infestation by the peach-potato aphid (Myzus persicae Sulzer, PPA). The response was studied in “Rubira”, a red-leaf cultivar resistant to PPA (Pascal et al, 2002) that shows strong level of induced resistance two days after infestation (Sauge et al, 2002) and “GF305”, a susceptible cultivar. Growing shoot apices, that are the preferred settling and feeding site of PPA, were sampled 48 hours after infestation and analysed for their 1H NMR profiles and their levels of main primary and secondary metabolites. Whereas no obvious differences were detected between metabolic profiles of infested and non-infested plants in the “GF305” susceptible cultivar, clear-cut changes in the 1H NMR and HPLC profiles were observed in Rubira following infestation. Carbohydrates and most organic acids showed a marked decrease. Several amino acids, including lysine and branched-chain and aromatic amino acids, showed a large accumulation whereas levels of glutamine, proline and threonine were greatly reduced. Infestation of Rubira by PPA also triggered accumulation of secondary metabolites, including phenolic and cyanogenic compounds. This first metabolomic approach of plant responses to infestation by an aphid species provides new insights into the metabolic pathways affected by insect feeding. Hypotheses on the mechanisms involved in induced resistance are discussed.