The population-balance framework of Kovscek, Patzek, and Radke is extended to model the flow of foam in porous media containing residual oil (Kovscek et al. Chem. Eng, Sci. 1995, 50 3783). A mechanistic rate of coalescence due to oil, based on the recently proposed pinch-off mechanism (Myers, T. J. Ph.D. Dissertation, University of California, Berkeley, CA), is included in the model. New foam-flow experiments in the absence and presence of residual oil in 1.1- and 0.28-mu m(2) Berea sandstone cores 60-cm long are modeled. Results reported here are for total superficial velocities of 30 cm/day and 97% foam quality with a 0.5 wt % sodium dodecyl sulfate 0.5 wt % NaCl aqueous solution, and a decane oil phase. Additional results at varying gas and liquid velocities are reported elsewhere. Agreement between experiment and simulation is good. Both experiment and simulation show that foam is destabilized by oil and has lower mobility in higher permeability media regardless of the presence of oil. These findings suggest that in an oil reservoir foam will preferentially flow through low-permeability oil-containing regions of the reservoir and partially block high-permeability oil-depleted regions as compared to a Newtonian fluid.