The phase behavior and oil solubilization capacities of a series of model microemulsion systems have been studied. Phase behavior was studied in systems composed of NaCl brine, sodium dodecyl sulfate, and either 1-butanol, 1-pentanol, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, ethylene glycol monohexyl ether, or diethylene glycol monohexyl ether. It was found that longer chained cosurfactant systems exhibit isotropic behavior over smaller compositional ranges. Whereas the ethylene glycol monohexyl ether system was found to possess two separate isotropic microemulsion-type regions, all other systems were found to possess connected isotropic regions. The one-phase regions in the 1-pentanol system, however, are connected by a narrow channel. Finally, it was determined that increasing the degree of amphiphilicity in the cosurfactant tends to increase the occurrence of liquid crystal phases.