Population parameters of the green peach aphid (GPA),Myzus persicae(Sulzer), were compared on potatoes fertilized with different levels of nitrogen (N) (56, 84, 140, and 224 kg N/ha). Abundance of GPA was not significantly different among N treatments. The population growth rate of GPA increased with the level of N applied. However, the highest level of N (224 kg N/ha) reduced the rate of population growth. Populations grew more rapidly on potatoes fertilized with a split-applied intermediate N treatment (56 + 84 kg N/ha) than on potatoes fertilized with 56, 56 + 28, or 56 + 168 kg N/ha. Additionally, populations of GPA grew more rapidly when 224 kg N/ha was applied in one application than when applied in two applications. The rate of population growth was positively correlated with the concentration of free amino acids in leaves. The within-plant distribution of GPA was similar for all treatments. GPA were consistently more abundant on the lower leaves in each treatment. Population growth rates were greater on lower leaves than on other leaves in most N treatments. Population growth rates were negatively correlated with foliar concentrations of free amino acids within leaves of different vertical zones, but were positively correlated with foliar concentrations of nitrate N within leaves of different vertical zones. Also, population growth rates were positively correlated with the percentage of the total organic N pool composed of amino N within leaves of different vertical zones. Implications of variable host-plant nutritional quality in pest management are illustrated.