Two model surfactant systems, one based on Texas 1 and the other on sodium dodecyl sulfate, were developed to give ultralow interfacial tensions and middle phase microemulsions when equilibrated with oil. Examination of their aqueous and microemulsion phase behavior, and comparison of the results with results of similar studies made on a system based on WITCO TRS 10-410, led to the conclusion that it is possible to generalize the phase behavior. The liquid crystalline spherulitic and lamellar textures observed in all these systems are the only homogeneous, non-phase separating fluids which can produce ultralow tensions on contact with oil. Mapping of the phase behavior of the two model surfactant systems showed that existence of the middle phase is relatively insensitive to surfactant concentration but quite dependent on cosurfactant concentration. Preliminary study of polymer-surfactant interactions confirmed the previously reported phase separation effect. A new temperature controlled polarized light screening device was built and has already been put to use for discrimination of isotropy, birefringence, scattering, and interfacial phenomena in systems of interest for enhanced oil recovery.