This paper give the optimum leaf contents of N, P, K, Ca, Mg and their ten binary ratios as a function of yield, in five different stage of the vegetative cycle of peach trees (Prunus persica L., Batsch). The optimum contents were selected as those leading to the highest yields, by using the calculation methodology described by Recalde, extended and improved with the SPSS computer program.This methodology has been applied to the nutrient contents and their ten binary ratios obtained from leaf samples taken 60, 90, 120, 150, and 180 days after full bloom. In separate calculations, correlations between each of the nutrient contents, binary ratios and yield have been performed. The following reference values are proposed: 60 days after full bloom: 3.84% N, 0.26% P, 2.68% K, 1.49% Ca and 0.61% Mg; 90 days after full bloom: 3.67% N, 14.02 K/P or 3.79 Mg/P, 2.69% K, 1.89% Ca and 0.73% Mg; 120 days after full bloom: 3.32% N, 0.16% P, 2.58% K, 2.05% Ca and 0.82% Mg; 150 days after full bloom: 3.01% N, 21.17 N/P, 2.80 K/Mg, 2.52 Ca/Mg and 0.84% Mg; 180 days after full bloom: 20.25 N/P, 0.15%P, 13.42 K/P, 2.57 Ca/Mg and 2.49 K/Mg.This paper is part of the CA 11/86 project funded by "The Consejo Asesor de Investigación" (Advisory Research Council) of Diputación General de Aragón.Peer reviewed