Total body concentrations of Pb and Cd in Porcellio scaber decreased with increasing distance from traffic as the main emission source. The highest concentrations of metals were found in woodlice collected in the vicinity of the expressway: 11.2 and 6.1 μg g^-1 dry weight (ppm) for Pb and Cd, respectively. Lower concentrations were measured in animals taken from the city park: 8.3 and 3.1 ppm, respectively. The lowest metal concentrations were present in woodlice taken from a nonexposed site situated within an oak forest: 3.5 and 0.2 ppm for Pb and Cd, respectively. To investigate toxicity effects of metal uptake, the metabolic rate (heat production) was measured. No significant differences could be found between the three groups. It seems, therefore, that present Pb- and Cd-pollution released by automobile traffic has no effect on the metabolic rate. In laboratory experiments, reduction of metabolic rates could only be observed in woodlice with total body concentrations of at least 20 ppm Cd and 50 ppm Pb.