The steam assisted gravity drainage (SAGD) process has been successfully tested in field pilots, and commercial applications are currently underway by a number of oil companies. The process yields higher oil rates and faster reservoir depletion, as compared to other in situ oil recovery processes. Current developments of the SAGD process are aimed at improving oil rates, improving oil-to-steam ratios "OSR," reducing energy, and minimizing water disposal requirements. In addition to SAGD, progress has been made in the development of solvent injection processes. These processes result in lower oil rates and energy, requirements as compared to SAGD. At the present time, limited field results are available for the solvent processes to allow for adequate evaluation of field performance. A novel approach for combining the benefits of steam and solvents in the recovery of heavy oil and bitumen has been undertaken at the Alberta Research Council (ARC). A newly patented Expanding Solvent-SAGD "ES-SAGD" process has been developed. The process has been successfully field-tested and resulted in improved oil rates, improved OSR, and lower energy and water requirements as compared to SAGD. The paper discusses the concept and laboratory testing of the ES-SAGD process.