An investigation was undertaken to establish the performance of a cobalt/manganese oxide catalyst in a fixed bed reactor for the conversion of carbon monoxide with hydrogen under conditions favouring the formation of gaseous, liquid and solid (i.e. wax) hydrocarbons. The cobalt/manganese oxide catalyst in the form of extrudates with a diameter of 3 mm was prepared by a co-precipitation method. The fixed bed reactor consisted of a single tube with a diameter of 21 mm, similar to tubes used in typical industrial scale Fischer-Tropsch reactors. The catalyst requires a fairly long stabilisation period and produced an industrially viable product spectrum. Significant water-gas activity was observed which is not normally expected for cobalt based catalysts under Fischer-Tropsch synthesis conditions. Increased pressure up to 2100 kPa suppressed the water-gas shift reaction and lowered the olefin production.