Hydrolyses of p-nitrophenyl hexanoate (PNPH) and diethyl p-nitrophenyl phosphate (Paraoxon) were carried out in mixtures of basic aqueous solutions and HFE-7200 (an isomeric mixture of perfluorobutyl and perfluoroisobutyl ethyl ether). Hexadecyltrimethylammonium bromide (CTAB), a perfluoroalkylpyridinium chloride surfactant, tetrabutylammonium salts, and colloidal particles of cross-linked copolymers of 2-ethylhexyl methacrylate and styrylmethyl(trimethyl)ammonium chloride dispersed in either the aqueous phase or the HFE phase were used to promote the reactions. In a pH 9.4 borate buffer, the surfactants and the aqueous colloidal particles were the most active for PNPH hydrolysis, the PNPH preferred the HFE phase, and the rates depended both on mass transfer of the PNPH from HFE to water and on the intrinsic rate of hydrolysis in the aqueous phase. In 0.10 M NaOH, CTAB and the aqueous colloidal particles were the most active for Paraoxon hydrolysis, Paraoxon preferred the aqueous phase, and the rates followed pseudo-first-order kinetics.