We present preliminary results from quantitative genetic analyses of tooth size variation in two outbred pedigreed populations, baboons and mice. These analyses were designed to test the dental field theory as proposed by Butler (1939), that there are three fields within the dentition: incisor, canine, and molar. Specifically we estimated the genetic correlation between pairs of linear size measurements. Results from the baboon analyses suggest that there may also be a premolar field that is only partially independent of the molar field proposed by Butler (1939). Analyses of the mouse data indicate that for mice, size variation in the incisors appears to be genetically independent of molar size. If the field theory is correct, future analyses on incisor data for the baboons will return similar results of genetic independence. Circumstantial evidence from the fossil record suggests that there will be at least some degree of independence between the anterior and postcanine dentitions of primates.