The hydrogenation of methyl oleate (methyl-9-octadecenoate) into oleyl alcohol (methyl-9-octadecen-1-ol) was studied in the presence of a bimetallic CoSn supported over a zinc oxide catalyst in a stainless steel batch reactor at 270 degreesC and 8.0 MPa. Zinc oxide can activate the carbonyl group and also the hydrogen by a possible heterolytic and homolytic dissociation of dihydrogen. The selectivity to unsaturated alcohol (oleyl alcohol) was significantly enhanced by adding tin to cobalt. The activity and the selectivity to unsaturated alcohols was maximum for an atomic Sn/Co ratio of 1, as for the CoSn alumina sol-gel catalyst. For all CoSn catalysts, the selectivity to unsaturated alcohols goes through a maximum for a surface Sn/Co ratio close to 2, the active species being a mixed Me-0-(SnOx)(2), where the oxidation of tin is close to 0. The reduction of CoSn solids with sodium borohydride increased the activity of the catalyst.