Improved crude oil recovery by chemical flooding has been shown to be dependent on the phase behavior and properties of the microemulsion systems formed when chemicals contact oil. In order to apply this technique for in situ recovery of bitumen from tar sands, it is essential to investigate those chemical formulations that will yield optimum microemulsion phase behavior under typical field conditions. This paper reports the effects of caustic concentration, salinity, and temperature on bitumen emulsification and phase behavior of the middle-phase microemulsion. An optimum NaOH concentration corresponding to a maximum middle-phase volume was attained at a pH of about 13, which is higher than those often reported for crude oils. In contrast to the observed effect of temperature, increased NaCl concentration enhances bitumen emulsification. An acceleration of phase equilibration was also achieved at higher salinity level. Explanation of these results is proposed using information derived from measurements of surface tension and UV absorbance of the caustic-rich phase.