Data in the literature on the toxicity and uptake of copper by soil invertebrates are contradictory. Copper toxicity and bioaccumulation studies were therefore performed using earthworms and oribatid mites. Field-simulating experiments in soil-filled plastic containers showed that earthworms try to escape moderately toxic situations and that they are much more sensitive than oribatid mites to temporary high Cu super(2+) concentrations in soils. The copper concentrations in the earthworms increased in response to the higher concentrations of the copper fraction extractable with 2.5% acetic acid in the soil. The worms died when the concentrations within their bodies exceeded about 100-120 ppm, calculated on a dry weight basis.