The friction and wear of toughened zirconia ceramics in self-mated sliding contacts in various liquid environments were investigated and compared with those observed in air. Tests were performed in distilled water, pure ethyl alcohol and synthetic silicone oil. A pin-on-plate tribometer with reciprocating sliding motion was used to carry out the experiments. It was found that the friction and wear characteristics of the tested pairs were significantly influenced by environment. The lubricated coefficients of friction in the range of 0.1-0.4 were found and wear was generally low. All three environments reduced wear of zirconia ceramics from about 10(-14) m3 N-1 m-1 in dry sliding down to about 10(-16) m3 N-1 m-1 at the tested temperature and load-speed conditions. The wear scars were examined by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) and the effects of the environment on wear morphology are presented in this paper.