The steam foam process has been applied in the oil fields since the late 19708. The mechanism of the process, however, is not known fully; particularly the detrimental effects of oil on foam, while known, are still unexplained. This hinders field application as the behavior of surfactants cannot be predicted under field conditions. Understanding the mechanisms of foam generation, stability, and mobility of foam to improve the development of field level projects has been the focus of the attention of many workers of the oil industry. Extensive laboratory studies have been carried out, mostly without oil but some with oil. This study falls in the later category. A one dimensional sandpack (6 ft X 2.15 in) model is used to investigate the behavior of four anionic sulfonate surfactants of varying chemical structure with steam. The study is performed with an crude oil at residual oil saturation of about 12 percent of the pore volume. The observed pressure drops across the various sections 01 .he pack are used to study the behavior of the surfactant. The tested surfactants vary in chain length, aromatic structure and number of ionic charges. A linear toluene sulfonate produced the highest strength foam in presence of the oil at residual saturations, as compared to the alpha olefin sulfonates. This is in contrast to the behavior of the surfactants in the absence of oil, where the alpha olefin sulfonates perform better. The reason for this change in behavior is the relative propagation rate of the foams produced by the surfactants. This conclusion is based on the observation that increase in propagation rate decreases the detrimental effect of oil; while the propagation rate is of little significance without oil. The disulfonate performed better in the presence of oil. The improvement in the performance is embedded in the propagation rate of these surfactants as the rate of propagation in this case is also high. But the true mechanism of improvement in the strength of the foam instead of deterioration needs further study.