Holes were drilled in natural oil sands and reconstituted oil-free sand cores mounted inside a specially designed triaxial cell to investigate the borehole stability under hydrostatic loading. Tests involving hot water circulation inside the drilled hole were conducted to explore the effect of thermal heating and erosion on the borehole deformation. In addition, bitumen was removed from the oil sands matrix using chemical solvent extraction to study any reduction in strength. The deformation and failure of the hollow oil sands cylinders were monitored and studied using a computer tomography scanning method.