The effect of a growth reducing cadmium concentration (5 μg ml−1) on the structure and ultrastructure of leaves, stomata and plastids of bush bean plants (Phaseolus vulgaris L. cv. Contender) grown on perlite was studied using light, transmission electron and scanning electron microscopy. The structural and ultrastructural alterations observed were not directly related to the average Cd content of the whole organs. In roots, where the highest Cd concentration was found, plastid ultrastructure was hardly affected, while in the upper parts of the plant the chloroplasts showed severe alterations. Disruption of chlorophyll synthesis and plastid ultrastructure was greater in young trifoliate leaves than in primary leaves. The effects of Cd toxicity on the structure and ultrastructure and their physiological implications are discussed in relation to Cd uptake.