Use of N-substituted pyrrolidones to promote the penetration of agrochemical active agents. The use of one or more N-substituted pyrrolidones of the formula (I), (I) wherein R signifies a linear or branched, saturated alkyl group with 3 to 6 carbon atoms, wherein in the alkyl group, hydrogen -H can be substituted by a methoxy group -OCH3, and wherein 1 to 6 hydrogens -H of the pyrrolidone ring can be substituted by methyl -CH3, to promote the penetration of agrochemical active agents in plants or in non-plant-based harmful organisms is described.