in this investigation, the preparation and gas selectivity characteristics of an 'ultrafine' composite ceramic membrane are reported. A dip-coating technique was used to prepare a thin selective membrane on a commercially available ceramic macroporous filter (SCT, France). The permeabilities of H-2, N-2 and CO2 were measured at temperatures of 25-470degreesC and average pressures of 1-2 bar. The separation Of CO2/N-2 binary mixtures was also performed. The separation factors for CO2 were found to be higher than that of the Knudsen separation mechanism at room and high temperature. The potential applications of these membranes to CO2 separation at these temperatures are discussed on the basis of measured selectivity values.