This report summarizes progress in a research effort to quantify the effects of nonuniform flow on displacement performance in CO{sub 2} floods. Results are reported in three areas: (1) effect of phase behavior in one-dimensional flow; (2) interaction of viscous instability and flow in heterogeneous porous media; and (3) detection and representation of heterogeneity. In the first area, the development of a new experimental apparatus for simultaneous measurement of phase compositions, viscosities, and densities is described. In the second area, partly-scaled experiments to study the effects of viscous instability in the presence of permeability variation are described. In addition, results of detailed simulations of the growth of viscous fingers in both homogeneous and heterogeneous porous media are described. In the third area, use of a combination of pressure transient and well-to-well tracer tests to detect the presence of reservoir heterogeneities is discussed. Also presented is a technique for calculation of the transient pressure response to large scale heterogeneities and an analysis of the pressure response of one- and two-dimensional composite reservoirs. Finally, results of calculations of the effects heterogeneity and capillary and viscous crossflow are reported. 170 refs., 139 figs., 11 tabs.