Given the recent interest in increasing heavy oil reserves in many countries, Colombia among them, interest has been created for in situ combustion as an alternative method to extract oil where other techniques, provided the reservoir conditions, are not feasible. Nevertheless, there exists a significant amount of experts that do not conceive the application of this technique in a field scale due to its precedents. This article tries to give the reader a different view of the technique from new theories and new ways of treating a complex process as this one. Considerations regarding recovery mechanisms are presented, as well as the origin and evolution of the technique, its variations, laboratory tests, guidelines for numerical modeling and some design considerations.