Zinc tolerance was investigated in five populations of Arabidopsis halleri (syn.: Cardaminopsis halleri) raised from seeds collected from contaminated and uncontaminated sites. Tolerance was measured by determining the concentration which inhibited root growth (EC100). A. halleri populations from contaminated and uncontaminated sites were found to be Zn-tolerant compared with the Zn-nontolerant species Arabidopsis thaliana and A. lyrata subsp. petraea. At very high Zn concentrations, populations of A. halleri from uncontaminated sites were slightly less Zn-tolerant than those from contaminated sites. These observations support the hypothesis that in A. halleri, Zn tolerance is largely a constitutive property. One population from an uncontaminated site and one population from a contaminated site were studied for Zn uptake. Zinc content was measured in shoots and roots using a colorimetric test under laboratory conditions. The results showed that whatever their origin, individuals from both populations are Zn accumulators compared with the nonaccumulator species A. thaliana. Moreover, the population from the uncontaminated area accumulated Zn in its shoots and roots more quickly than the population from the contaminated site. These results suggest that, in A. halleri, Zn accumulation to very high concentration is a constitutive property.