The law of allometry, y = bxα, was applied to measurements on the skulls and limb bones in twenty-eight modern breeds of dogs. The data conform to the equation, yielding in some cases a single curve including all the breeds, and in others two or more distinct curves. On the basis of these results, the various breeds of dogs may tentatively be classified into six allometric tribes, each characterized by the fact that for any given relation all its members form a single curve conforming to the law of allometry. This conformity is interpreted as indicating that the breeds within a tribe are genetically relatively homogeneous with respect to ontogenetic relative growth. According to the available evidence, the proposed classification is valid also for ancient and prehistoric types of dogs. The European wolf, however, does not fit into any one tribe. For the same relation in different tribes, the values of b in all cases conform approximately to a decreasing exponential function of α.