Summary.Two means of reducing soil contamination resulting from the leaching of spray residues of dalapon from plant foliage were tested: use of volatile forms of the herbicide, residues of which slowly evaporate from the foliage; and use of formulations that congeal to a solid film to retain the herbicide against leaching. Rates of evaporation from glass slides at 20° C for the ethyl ester,nbutyl ester, acid, and diethyleneglycol bisester of dalapon were respectively 15, 1‐6, 0′27 and 0.01 mg/cm2. As foliar herbicides the ethyl and butyl esters were ineffective and the acid of limited effectiveness due to rapid evaporation. The glycol ester was as effective as the sodium salt. With its evaporation rate of approximately 1 kg/ha/hr at 20°C, application of dalapon in the form of the diethylrneglycolbisester is considered promising as a means of limiting soil contamination. Mixtures of the diethyleneglycolbisester of dalapon with polyvinylacctate emulsion dry to form films that greatly reduce leaching of the herbicide at the expense of minor reduction in herbindal activity. Such formulations afford a means of limiting soil contamination.Formulation du dalapon pennettant de rédiuire la contamination