The factors influencing the local distribution of Peromyscus leucopus and Zapus hudsonius were studied in seven habitats (old field, hardwood swamp, coniferous swamp, bog mat, spruce burn, upland hardwood, and grass sedge marsh) in southern Michigan. The environmental factors considered were vegetation type, cover (fallen trees, brush, leaf litter), temperature, food, moisture, and interspecific competition. P. leucopus permanently inhabited only wooded habitats (those with trees or shrubs). There was no indication of an avoidance of herbaceous vegetation; there appeared to be a positive response to a tree-shrub type of vegetation. The reason for such a response was not determined. Among the forested areas, an oak-hickory upland was the most favorable habitat. A larger and more stable food supply (acorns and nuts) appeared to be the major factor responsible for the greater abundance of P. leucopus in this habitat. Temperature, moisture, cover, and interspecific competition were not important factors in the selection or avoidance of a particular habitat. Z. hudsonius was found only in moist situations and was slightly more abundant where there was standing water. Vegetation, temperature, cover, and interspecific competition were not important factors in its local distribution. During the course of a field study of the local distribution of microtine rodents and shrews in southern Michigan, data were obtained pertaining to the white-footed mouse. Peromyscus leuco pus, and the jumping mouse, Zapus hudsonius. Although the study was not designed primarily for these two species, there was sufficient variation in the habitats to determine the influences of certain factors. Since information concerning the local distribution of small mammals is relatively rare in the literature, it seems advisable to make these data available. The information presented in this paper has been extracted from a thesis presented in partial fulfillment of the degree of Doctor of Philosophy in the University of Michigan. DESCRIPTION OF THE STUDY AREA AND METHODS Study area.-All the work was done in the University of Michigan's Mud Lake Research Area in southern Michigan. Seven habitats (old field, hardwood swamp, bog mat, spruce-birch-larch swamp, spruce burn, oak-hickory upland, and marsh) within the area were selected for study. In addition, six transects were established to cross as many types of habitat as possible. The study areas and transects are described in detail elsewhere (Getz, 196ta, b). Methods.-Three methods of sampling the abundance of small mammals were utilized. (1) A rectangular study area consisting of 75 trap stations placed in a grid pattern with an interval of 12 meters