Summary.The adsorption of acid, n‐butyl, and iso‐octyl ester forms of 2,4‐D (2,4‐ dichloiophenoxyacetic acid) was studied for several Canadian prairie soils. Thekvalues for the acid ranged from 0·09 to 1·30 and were correlated to the soil organic matter and not to the clay content. TheQ, values (μg adsorbed/g of organic matter) for the acid were 7–2±l. The n‐butyl and the iso‐octyl esters hydrolysed to the acid form in the aqueous medium and this process was accelerated in the presence of the moist soil. Consequently, thekvalues for the esters, using slurry type adsorption experiments, or their distribution coefficients, using leaching columns, could not be determined. It was concluded that the adsorptive behavior of the two esters in moist soil was similar to that of the acid form.Comportement des formes actde, et ester du 2,4‐D quant à leur ads