Abstract.1The amino acid content of phloem exudates from leaves and of aphid honeydew were adopted as indices of the nutritional quality of phloem sap for aphids. Four plant species and associated leaf‐dwelling aphids were investigated: the sycamoreAcer pseudoplanatusand sycamore aphidDrepanosiphum platanoides; Prunus domestica(victoria plum) and the mealy plum aphidHyalopterus pruni; and the spindle treeEuonymus europaeusand broad‐beanVicia faba, both hosts of the black bean aphidAphis fabae.2The concentration of amino acids in the phloem exudates varied with: (a) plant species (greater in the herbViciathan in the tree species), (b) season (greater in the autumn than summer forAcerandEuonymus), and (c) position (greater in flush leaves than mature leaves ofPrunus).3ForAcerandPrunusand their aphids, the concentration of amino acids in phloem exudates was significantly correlated with the amino acid content of the aphid honeydew.4The amino acids in all exudates and honeydew were dominated by non‐essential amino acids (glutamic acid, glutamine, asparagine or serine, varying with season and between plant species). The sole major discrepancy between the amino acid profiles of exudates and honeydew was the production of asparagine‐rich honeydew by aphids feeding on leaves, whose exudates were dominated by glutamic acid; this applied to bothH.prunion maturePrunusleaves andDrepanosiphum platanoideson summer‐leaves ofAcer.5It is suggested that EDTA‐exudation may be a useful technique to study nutritional correlates of aphid life cycles, e.g. the time of migration between primary and secondary