We present an analysis of the displacement properties during the dynamic invasion of steam in a porous medium. Two fully developed regimes are identified, similar to the Stabilized Displacement (SD) and the Capillary-Viscous Fingering (CVF) regimes of the isothermal drainage problem (Yortsos et ah, 1997). Phase change and heat transfer affect the scaling of the various properties of these regimes. Near the advancing steam front, phase change and heat transfer bring about a qualitative change in the flow permeabilities, although not in the displacement pattern, which remains of the Invasion Percolation type, if injection rates are sufficiently small. The relative permeabilities in this region are larger than those for the isothermal displacement problem. A condition is developed to delineate the regions of validity of these two regimes.