Results of a comprehensive research effort to identify, investigate and quantify factors which influence CO/sub 2/ flood performance are presented. Results of static equilibrium phase behavior experiments for mixtures of CO/sub 2/ with Wasson crude and Wasson oil containing varying amounts of solution gas are reported for three temperatures, 90, 105 and 120/sup 0/F. Analysis of the resulting phase diagrams suggests a simple correlation for minimum miscibility pressure (MMP) based on the vapor pressure of CO/sub 2/, extrapolated if necessary for temperatures above the critical temperature of CO/sub 2/. Results of phase behavior experiments with the same oil and CO/sub 2/ contaminated with nitrogen are also reported, and a simple procedure for estimating the effects of changes in system temperature or contamination of the CO/sub 2/ on MMP is offered. Results of detailed measurements of phase compositions in CO/sub 2/-hydrocarbon systems are presented. The theory of the effect of CO/sub 2/-crude oil phase behavior on displacements in an ideal porous medium is tested by predicting the performance of slim tube displacements from independently measured phase behavior and fluid property data obtained with the continuous multiple contact experiment. The quantitative agreement between prediction and experiment is good enough to suggest that the essentials of CO/sub 2/-crude oil phase behavior can be modeled with a small number of pseudo-components. Modifications to the simulator to model effects of dendritic and trapped saturations are described. Calculated composition paths for both secondary and tertiary displacements indicate that microscopic limitations to mixing, due to heterogeneity of the rock or to the presence of water, adversely affect local displacement efficiency. 126 references, 170 figures, 28 tables.