The objective of this study was to evaluate the relative effects of Ca, Mg, and K on the adsorption of Zn and Cu by several Florida soils under citrus production and to differentiate the specific cation effects vs. effects of ionic strength on adsorption of Zn and Cu. A batch-equilibration technique was employed to evaluate the adsorption of Cu and Zn (added at 10−4M) in the presence of varying concentrations of Ca or Mg (2.5–15 mmol) or K (5.0–30 mmol). Adsorption of both Cu and Zn decreased with an increase in concentrations of either Ca or Mg. The inhibitory effects of added cations on the metal adsorption was much greater for Zn than for Cu. Addition of K slightly decreased the adsorption of Zn but had little effect on Cu. The inhibitory effects of Ca and Mg on the adsorption of Cu or Zn appear mainly due to competition for the exchange sites on soil colloids.