Although the idea of injecting gases to improve oil recovery has been known for over three-quarters of the past century, it appears to be taking on a new meaning as we step into the new millennium. The oil price scenario remains consistently loyal to its roller-coaster past; the long awaited jump in the natural gas price has become a reality; the oil industry has made new strides in horizontal drilling with significant cost reductions; and the world's attention is focused on the industrialized nations to lead the way to control global warming by reducing greenhouse gas emissions. These evolving global issues combined with the ever-declining reserves of conventional crude oils appear to bring a new optimism to enhanced oil recovery (EOR) by gas injection. Added to this optimism are the well-accepted facts that waterflood recovery from conventional oil reservoirs rarely exceed 40% of the original oil in place (OOIP); that most waterfloods are maturing or close to their economic limits; and that chemically enhanced waterfloods appear to have become practically extinct in spite of their conceptual soundness. Therefore, gas-based EOR processes using horizontal wells appear to be the solitary hope for continual:profitable production from the large remaining reserves of conventional oil in Canada, the United States and the rest of the world. In what follows, we will briefly discuss-but not review the conceptual basis for gas injection EOR processes and what, we, have conveniently overlooked in it, the historical developments, process design considerations, problem ar eas, and the future direction and potential of this time-tested technology.