Results are presented on the development of a new procedure for the preconcentration and analysis of the eleven phenolic compounds covered by the E.P.A. 604 method. This new procedure is applied to synthetic sea water samples, previously adjusted to pH 2, using stearylamine and hexadecyltrimethylammonium bromide as surfactants and concentrating the pollutants in a small volume of di-isopropyl-ether. Experimental conditions have been optimized by means of a procedure previously published by the authors, that makes use of the simplex algorithm. Under the final conditions established recoveries for the investigated compounds range within 80–95 %, except for phenol, only 60 % of which is recovered.