Paraffinic oil, Me ester of rapeseed oil-derived fatty acids and 2 organosHicone surfactants were added as adjuvants to corn. 2,4-dichlorophenoxyacetic and 3,6-dichloro-2-methoxybenzoic acids - contg. herbicide spray liqs. They were than studied for surface tension, crit. micelle concn., contact angle as well as for biol. activity on spring oilseed rape (Brassica napus var. oleifera L). The highest increase in the herbicide activity was obsd. when the Me ester of rapeseed oil-derived fatty acids was used.