Per capita population growth rates (r) of the aphidsAphis gossypiiGlover on cucumber (Cucumis sativusL. ‘Vetomil’) andMyzus persicae(Sulzer) on pepper (Capsicum annuumL. ‘Midal’) were compared on plants provided varying concentrations of nitrogen (N) in nutrient solutions. ForA. gossypiion cucumber, treatments included a solution first at 90 then at 175 ppm N, a constant 175, and a constant 225 ppm N solution. The rate of population growth ofA. gossypiiwas Significantly lower on the 90–175 ppm N solution than on either the 175 or 225 ppm N solution, which were nearly equal. The mean time to first offspring was significantly longer for aphids on cucumber provided the 90–175 ppm N solution than on 175 ppm N. Higher fecundity was observed for aphids on plants provided 175 and 225 ppm N.A. gossypiisurvivorship was shorter in the 90–175 ppm N treatment than in the higher N treatments (x2= 6.7,P= 0.04). At the time aphids were placed on the plants, the percentage N in leaves was significantly lower in the 90–175 ppm N treatment than in the other two treatments (P<0.01).The solutions provided to pepper plants were a 60 ppm N solution in the vegetative, 90 in the early fruit, and 120 in the late fruit stage, a constant 120 ppm N and a constant 175 ppm N. Ther-values forM. persicaeranged from 0.31 to 0.36 and increased with N concentration (experiment 1,P= 0.05; experiment 2,P<0.02). The higherr-value for aphids in the 175 versus 120 ppm N in experiment 1 was caused in part by a significantly shorter time to production of first offspring (P<0.01). In experiment 2, the time to production of first offspring was the same in the 120- and 175-ppm N treatment, but higher fecundity was observed in the 175 ppm N treatment. Percentage foliar N increased significantly with each increase in N provided in the nutrient solution (P<0.01).