Peripheral capture locations have been used traditionally for predicting biological range limits. Maps based on these data may be inaccurate and may not provide useful information regarding the ranges of endangered species. A method was presented for predicting probable ranges of mammals based on the distribution of environmental factors associated with areas where animals have been known to occur. These factors were determined primarily from the literature. They were assigned relative weights based on frequency of occurrence in the literature. Computer technology was used to analyze an existing database stored at a cellular level to describe the probable distribution of the factors over large areas. Geomorphological, topographic, land-use, and physiographic data were included in the analyses. The method was applied to three mammals endangered in Virginia -- water shrew (Sorex palustris), northern flying squirrel (Glaucomys sabrinus), and Indiana bat (Myotis sodalis). Computer maps were produced showing the distribution of areas potentially favorable to each species in one of two study areas in Virginia. Maps produced by this method provide more information about ranges and range dynamics than tbos€ produced by traditional methods. Specifically, areas least likely to be favorable are shown as are those more likely to provide conditions suitable to the continued existence of the animal. Maps produced by this method may be useful for initial identification of critical areas, preliminary planning activities, endangered species management generally, and multiple range analyses. The method may be useful for range analyses of non-endangered species whenever information about range dynamics is needed.