Copper and zinc were separated from their hydroxides and mobilized out of contaminated sandy loam and lake sediment when the metals were in the presence of ammonia concentrations ranging, from 0.1 mol/L to 0.3 mol/L. In the equilibrium leaching experiments with pure hydroxides, the 2 heavy metals were mobilized by ammonia complexation in low-alkaline regions in a manner dependent on the total ammonia concentration. Within the pH range studied, the major metals present in the soils either remained practically immobile in the solid matrix (Fe) or their solubility was not directly influenced by ammonia complexation (Ca, Mg). In all cases, the maximum local increase in both zinc and copper solubility was observed at pH approximate to 9.5.