The effect of zinc on growth and reproduction of the springtail Folsomia candida has been determined for individual animals exposed to contaminated food. Zinc caused a decrease in growth of the springtails, which resulted in a decrease in the estimated final fresh weight at the highest exposure level (20 mg/g dry food). Other effects were observed from 5 mg/g dry food and included an increase of the juvenile period, an increase of development time, a reduction in first-clutch size and egg viability, and a reduction in the number of individuals reaching the reproductive state. The effect of these changes on the population growth rate was evaluated using an estimated value for mortality in the field. In the present analysis, the juvenile period was the most sensitive variable.