The silicon-sapphire interface of CVD silicon on a (11̄02) sapphire substrate has been studied by high-resolution transmission electron microscopy. Cross-section images of the interface are presented where the silicon and sapphire lattices are directly resolved. The images show that the interface is planar and abrupt to the limit of resolution (less than 3 Å). Defect anisotropy is evident and can be linked to tilt of the [100] direction of the silicon layer with respect to the normal to the substrate.