Progress of a comprehensive research program to quantify factors affecting CO/sub 2/ flood displacement efficiency is described. Experimental and theoretical investigations of the interactions of factors such as phase behavior and fluid properties of CO/sub 2/-crude oil mixtures, and heterogeneities in reservoir rocks are discussed. Literature on the interpretation of miscible displacements in one- and two-phase systems is reviewed. Simple displacement experiments to evaluate effects of core hteterogeneities and high mobile water saturations are described. Results of miscible displacement experiments with fluids of matched density and viscosity are presented and compared with results of a few displacements in which fluid properties were not matched. Those comparisons clearly indicate that control of viscous fingering is required if short core floods are to be interpreted with reasonable certainty. Detailed results of investigations of the phase behavior of CO/sub 2/-crude oil mixtures are presented. The volumetric behavior of mixtures of CO/sub 2/ with dead oils from the Wasson and Maljamar fields are compared with that of a Maljamar recombined reservoir fluid. The results provide the basis for a qualitative analysis of the effects of the presence of solution gas on CO/sub 2/ flood performance. Modifications to improve the continuous multiple contact experiment, which efficiently measures phase compositions and fluid properties, are described. An analysis of the operation of the apparatus is given for binary systems. The theory is compared with experimental results for CO/sub 2/-decane displacements, with excellent agreement. Extensive results of experiments to measure compositions and densities of phases present for CO/sub 2/-crude oil mixtures are reported. Finally, formulation of a mathematical model which considers the relative importance of factors such as phase behavior, fluid property variations, heterogeneity, and viscous and gravitational instabilities is discussed.