Effect of low-temperature degradation of 3Y-TZP ceramics (polycrystalline zirconia stabilized by 3mol% of yttria) on contact damage resistance has been studied applying scratch testing technique. Friction properties and damage mechanisms have been investigated for various degrees of hydrothermal ageing, i.e. for different grain sizes and crystallography, and for different thickness of the degraded surface layer. The onset of plastic damage, catastrophically cracking, grain pull-out, spalling and chipping due to top layer debonding have been identified. The contact damage micromechanisms corresponding to various degrees of degradation have been studied in detail by interferometry and microscopy.