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Chronic toxicity experiments were performed using the collembolan Orchesella cincta (L.) and the oribatid mite Platynothrus peltifer (Koch), which were exposed to various levels of cadmium in the food (green algae). Experimental results were combined with life-history information to obtain realistic estimates of the intrinsic rate of population increase and its sensitivity to Cd stress. Chronic LC50 values for dietary exposure to Cd were estimated as 1.60 μmol/g for O. cincta and 3.18 μmol/g for P. peltifer. No-observed-effect concentrations (NOECs) for growth and reproduction were 0.042 μmol/g for O. cincta and 0.026 μmol/g for P. peltifer. The main effects of Cd were, however, different in each species. In O. cincta, Cd affected primarily female growth, without a direct effect on reproduction; in P. peltifer, the effect was primarily on reproduction. Uptake of Cd was higher in P. peltifer than in O. cincta, and caused a loss of …