A supported aqueous-phase, asymmetric, hydrogenation catalyst, SAP-Ru-BINAP-4SO3Na, is synthesized. Impregnation of water from an organic phase, ethyl acetate, is used to hydrate the SAP catalyst. Both the activity and enantioselectivity for the asymmetric hydrogenation of 2-(6’-methoxy-2’-naphthyl)acrylic acid to naproxen are found to be dependent on the water content. Maximum activity and e.e. are observed when water-saturated ethyl acetate is used to hydrate the SAP catalyst, an initial turnover frequency of 18.2 hr-1 and a 70.0% e.e. at room temperature under approximately 1350 psig of hydrogen pressure. At similar conditions, initial turnover frequencies of 131 and 0.34 hr-1 are observed from Ru-BINAP-4SO3Na in homogeneous (methanol as solvent) and two-phase (water-ethyl acetate) reaction systems, respectively. Although an excellent 96. 1 % e. e. (at 4-degrees-C and 1230 psig of H-2) iS found in neat methanol (homogeneous), the enantioselectivity of the SAP catalyst (up to 70% e.e.) is bounded by the intrinsic enantioselectivity limit of the ruthenium complex in water. Recycling of the SAP catalyst is easily achieved without any leaching of ruthenium into the organic phase.