Arsenite sorption was investigated in three Spanish soils. The form of the equilibrium curves of arsenite sorption confirmed that the isotherms of this process pertained to the L class of Giles classification. The curves corresponding to Soils 1 and 3 could be included in the subgroup 1 (monolayer coverage) and the curve of Soil 2 pertained to subgroup 4 (two centers of sorption). The Freundlich equation successfully described As(III) sorption over the entire As(III) concentration range in all the studied soils. Sorption of arsenite increased with increasing temperature; however, this increase was likely caused by an effect on the rate of the diffusion reaction that follows the adsorption process.