This paper investigates variation in folk medical beliefs in a Tarascan community in west-central Mexico. The data are from a structured interview completed with ten traditional curers and a like-sized comparison group of noncurers. Three possible patterns of interinformant agreement are described and tested using the quadratic assignment program. The results suggest that although curers and noncurers do differ, the differences are not so great that they represent two variant systems of medical beliefs. Rather, there is a single system of beliefs common to both groups, but with curers showing higher agreement among themselves in expressing this system than noncurers. This finding, and a related one showing higher agreement among older informants, are explained in terms of culture learning. Curers and older people share more knowledge about illness because of their greater experience in both dealing with and communicating about illness. A model of folk medical knowledge is then presented and systematic variation from this model examined.