Friction and wear of sapphire and steel counterfaces sliding on unlubricated thin films of zirconia were studied using conventional multiple pass pin-on-disk testing and single pass testing with a 'friction microprobe'. The zirconia films were grown by electron-cyclotron-resonance (ECR) oxygen plasma assisted deposition on r-cut (01 (1) over bar 2) sapphire using different growth parameters to produce films with varying degrees of order. The microstructure of the zirconia films is correlated to the widely varying observed friction and wear characteristics. Anisotropic stress effects produced during scratch tests are also presented.