Various magnesium phosphates were tested as catalysts for the vapour-phase Meerwein-Ponndorf-Verley-Oppenauer (MPVO) reaction between 2-hexanol and cyclohexanone. Some of the solids studied are as selective as MgO in this reaction. Others are also active in the dehydration of the alcohols. The activity and selectivity of the catalysts are related to their structure and surface chemical properties.