Low-speed friction tests with fine diamond styli and spherical sliders of ruby, sapphire, and hardened steel were carried out on the crystallographically prominent planes of synthetic single-crystal rutile at room temperature. The friction against diamond was 0.04–0.10; against sapphire and steel, 0.10–0.15. Ploughing friction was found to be anisotropic. When larger sliders were used so that the contribution by ploughing was minimized, the frictional anisotropy vanished. The anisotropy of ploughing was correlated with plastic deformation by slip in and adjacent to the friction track, as seen and studied with the optical microscope. Surface damage by cleavage and brittle failure was found to be severe during the friction experiments.Presented as an American Society of Lubrication Engineers paper of the ASME/ASLE Lubrication Conference held in Atlantic City, New Jersey, October 8–10, 1968.