The nature and extent of surface damage in 6H-SiC substrates prepared by mechanical polishing have been studied using backscattering of ultraviolet light and cross-sectional transmission electron microscopy. When the basal plane surface is prepared by lapping or polishing with large size diamond abrasives, the surface roughness is about one-fifth the ping or particle size, while the subsurface damage extends to a depth of about half the abrasive size. Under optimum conditions of particle size, vertical load, and relative rotation speed, the extent of subsurface damage can be minimized resulting in a nominally defect-free specular surface exhibiting a uniform strained layer of less than 8 nm.