The interfacial activity of 2-hydroxy-5-l-butylbenzophenone (E)-oxime (HBBO), two model a-acyloin oximes: 9-hydroxy-8-hexadecanone oxime (HHO) and 13-hydroxy-12-tetracosanone oxime (HTO), and a model modifier such as p-tertbutylphenol (BPh) is investigated at toluene/ water interface, at 21°C. Interfacial tension isotherms for individual compounds as well as for binary mixed solutions are obtained. In particular, it is shown that in all mixed systems co-adsorption is observed. Composition of mixed adsorption monolayer is affected mainly by mutual efficiency of adsorption of surface active components and composition of the bulk solution phase.