Experimental evidence is adduced for the view that rubber friction is similar in character to viscous flow and therefore, in contrast to solid friction, not necessarily accompanied by abrasion. This theory implies that the forces of rubber friction are proportional to the true area of contact. The true area of contact is determined by elastic deformation of the asperities on the rubber surface, with the result that Amontons' law is not obeyed by rubber. The laws of rubber friction are deduced from simple models and satisfactorily confirmed by experiment. Abrasion of rubber is due to mechanical failure under the tractive stresses produced frictionally by the asperities of the track. In this process, certain periodic structures are often created on abraded rubber which have been called “Abrasion Patterns”. Abrasion patterns are found to increase the rate of abrasion; a distinction is therefore made between “Intrinsic Abrasion”, occurring in the absence of patterns, and “Pattern Abrasion”. Both types of abrasion are treated theoretically, and qualitative agreement with the experimental results is obtained. The phenomenon of pattern abrasion has the important consequence that the relative abrasion rating of any two compounds can depend pronouncedly on the conditions of the test.