It is estimated that there are 85-110 billion barrels of heavy oil reserves in the U.S.. Since the 1960's, steam has been the predominant Enhanced Oil Recovery (EOR) method for these high viscosity, heavy oil reservoirs world-wide. However, some experimentation utilizing immiscible carbondioxide injection in heavy oil reservoirs has shown encouraging results. This paper documents the efforts of a 2-1/2 year, two phase project conducted in the Midway-Sunset field of California applying a novel steam/carbon-dioxide combination process to reeover heavy oil.