The two major difficulties in producing petroleum from subsurface formations by fluid injection are poor displacement efficiency and poor sweep efficiency. Engineering and chemical means are being investigated to improve the performance of these recovery controlling processes. The need for improving the recovery of petroleum from known oilfields becomes obvious when it is realized that on the average only about one‐third of the oil originally in place at the time of discovery is ever produced. This fact coupled with the fact that our nation uses about 18 million barrels of petroleum per day while producing less than half this amount emphasizes the need for this improvement. Interfacially active compounds suitable for oilfield application now are available for use. Similarly, polymers of various kinds also are available in quantities sufficient for use in petroleum recovery. The utilization of these kinds of materials will be discussed together with the desired effects and limitation of their use for oil recovery purposes. The chemical and physical principles of the newest enhanced oil recovery processes that are currently under development by the Government and the petroleum industry will be discussed.