Research on gas flooding and miscible displacement, with an emphasis on improvement of CO/sub 2/ flood performance is described. Low reservoir volumetric sweep efficiency is the major problem associated with gas flooding and all miscible displacements. CO/sub 2/ flooding would be considerably more efficient if a larger area of the reservoir could be contacted by the gas. Current research has focused on mobility control, computer simulation, and reservoir heterogeneity studies. Three mobility control methods have been investigated: the use of polymers for direct thickening of high-density carbon dioxide, mobile ''foam-like dispersions''of carbon dioxide and aqueous surfactant, and in situ deposition of chemical precipitates. 17 refs., 22 figs., 8 tabs.