The localization of 65Zn was examined in cell-free systems extracted from the roots of clones of Agrostis tenuis in further investigations on the mechanism of heavy metal tolerance in this grass species. The cell wall fraction was a major site for zinc accumulation especially in a zinc-tolerant clone where more zinc accumulated at this site than in non-zinc-tolerant clones. In the absence of the cell wall fraction or when its zinc-binding potential had been reduced, other particulate cellular components accumulated large amounts of zinc. Zinc uptake by the cell wall occurred by the same process in all the clones studied. Uptake was very rapid and independent of temperature and pH, suggesting an exchange adsorption process. A basis for zinc tolerance in A. tenuis is briefly discussed.