In this study effects of the preparation method on the characteristic properties and CO oxidation activities of Ag2O/Co3O4 catalysts were investigated. Catalysts were prepared by two different methods: sol gel and co-precipitation. N-2 physisorption measurements, X-ray diffraction, and scanning electron microscopy measurements were used to characterize the catalysts. CO oxidation activity tests were carried out under 1% CO, 21% O-2, and the remainder He feed condition between 20 degrees and 200 degrees C. According to the N-2 physisorption measurements, catalysts prepared by the co-precipitation method have a higher surface area than the catalysts prepared by the sol-gel method. Co3O4 and AgCoO2 phases were obtained from catalysts prepared by both techniques. In addition to these phases, metallic silver peaks were obtained by increasing calcination temperature. SEM micrographs of the catalysts showed that catalysts have uniform particles. Increasing the calcination temperature caused the formation of different-sized agglomerates and an increase in the gaps between agglomerates. The best activity was obtained from the Ag-2 O/Co-3 O-4 catalyst calcined at 200 degrees C and prepared by the co-precipitation method. This catalyst gave 50% CO conversion at 106 degrees C. The other two catalysts gave 100% CO conversion at a higher temperature of 200 degrees C.