Abstract: A process for in situ recovery of a tar sand deposit located beneath the earth's surface. A number of boreholes are drilled laterally from subsurface tunnels into the lower portion of the tar sands formation. Initially as a displacing means such as steam is injected into the boreholes, the tar sands become viscous and gravity flow into the bottom of the boreholes. Continuing to apply steam removes the tar sand deposits located in interstitial crevices between the boreholes thereby allowing the steam to flow laterally through these interstitial crevices to nearby boreholes. The steam rises toward the upper portion of the resource formation to create a horizontal heated plane of steam to further remove tar sand deposits located therein.