Direct comparisons between steam-water and air-water capillary pressures have been few because of the difficulty in experimental measurement. An experimental method was developed to measure both steam-water and air-water capillary pressures using an X-Ray CT technique. Spontaneous water imbibition and gravity drainage tests were conducted in ceramic core samples for steam-water and air-water systems, respectively. The results were compared, and it was found that the steamwater capillary pressures were less than the air-water capillary pressures.