Changes in ascorbic acid, total indoles, tannins, total carbohydrates and amino acids in resistant (Nemaguard, Nemared and Okinawa) and susceptible (Meetghamr) peach rootstocks grown in two types of soil and infected with the root-knot nematode, M. incognita were assessed. Roots and leaves of the resistant rootstocks grown in sandy soil had higher contents of ascorbic acid than the susceptible, Meetghamr. Leaves of all rootstocks had higher amounts of indoles than roots, seedlings grown in clay than those grown in sandy soil. Resistant rootstocks had percentages of tannins in their roots higher than the susceptible one and vice versa in leaves. Nematode infection resulted in increasing ascorbic acid, indoles and tannins contents and the highest percentages of increase was, in most cases in the susceptible rootstock, Meetghamr. No distinct variations could be observed between the susceptible and the resistant rootstocks in their contents of carbohydrates. In contrast, nematode infection decreased carbohydrate contents and the highest reduction was in Meetghamr.                 Fifteen amino acids were present in roots and leaves of different peach rootstocks. Roots of the susceptible rootstock either healthy or infected grown in sandy or in clay soil had higher values of amino acids than the resistant ones especially aspartic, serine, glutamic, valine and arginine. Nematode infection slightly decreased the amounts of amino acids except few cases and rates of amino acids reduction varied according to rootstock. Such  biochemical changes are, in part, involved in the resistance of peach rootstocks.