In recent years, MgO single crystals of brittle materials have been used widely in materials of high-temperature superconductivity, thin-film substrates and laser parts, but it is difficult to grind such crystals because of their brittleness and crack generation. Therefore, a super-abrasive diamond wheel is required for the mirror-like grinding of these materials. An optimum in-process electrolytic dressing system was constructed and the characteristics of the mirror-like grinding of MgO single crystals were studied with various metal-bonded super-abrasive diamond wheels. It is found that a finer super-abrasive wheel is prefable in obtaining the mirror-like grinding and surface grinding without cracks, with MgO single crystals. (C) 1997 Elsevier Science S.A.