The membrane extraction of phenol with linear monoalcyl cyclohexane (IMACH) as an organic solvent was studied. The organic/water distribution coefficient was obtained simply by equilibrating an aqueous solution of phenol with IMACH in a separatory funnel at room temperature. The mass transfer coefficient of phenol in the solvent extraction process was determined using the method of defined interface surface area. The membrane extraction of phenol was carried out in a commercial capillary dialyzer with a membrane surface area of 1.2 m(2). It was shown that a relatively high extraction efficiency could be achieved (over 90%) in spite of a relatively low distribution coefficient for the observed system (0.27) when the flow rate of the organic phase was higher than the flow rate of the aqueous solution of phenol.