Myodystrophy (myd) is an autosomal-recessive mouse mutation with dystrophic skeletal muscle. We propose that myd may be a model of the human disorder facioscapulohumeral dystrophy (FSHD) on the basis of clinical features and homologous genetic map locations. FSHD maps to human 4q35, while myd maps to mouse chromosome 8. To explore the relationship between FSHD and myd, it is necessary to define the homologous regions of human chromosome 4 and mouse chromosome 8, and ultimately, identify the genes underlying both disorders. A kallikrein gene (KaL3) was previously mapped by in situ hybridization to mouse chromosome 8 and human 4q35. We report the genetic map location of Kal3, bringing to 4 the number of genes with homologues on human 4q31-35 placed on the genetic map of mouse chromosome 8. As a first step in gene isolation, we have narrowed the interval containing myd by typing 125 affected mice with microsatellite markers. Analysis of recombinants placed myd in an interval that is flanked by genes with homologues in human 4q.