In a gravity stabilized thermal miscible displacement process for recovery of normally immobile high viscosity hydrocarbons in a subterranean formation, a steam and solvent vapor mixture is injected into the top of the formation, thereby establishing a vapor zone across the top of the formation. The steam and vapor mixture is lean or undersaturated in solvent vapors. The steam vapors condense to give up heat and raise the temperature of the underlying viscous hydrocarbons, thus reducing the viscosity thereof. The solvent vapors condense and go into solution with the viscous hydrocarbons, further reducing the viscosity thereof enabling the hydrocarbons to drain under the force of gravity into an adjacent production well completed at the bottom of the reservoir and where the hydrocarbons are recovered. The pressure at the producing well is controlled so that the pressure differential through the formation is approximately equal to the gravity head of the liquids in the formation.