Ecologic studies of small mammals in Rocky Mountain National Park (RMNP) were conducted in 1974 in order to identify the specific habitats within the Lower Montane Forest that support Colorado tick fever (CTF) virus. Data was collected on the abundance and distribution of 4 primary rodent species, tick infestation, CTF virus, and neutralizing antibody prevalence. Rodents were captured along transects crossing different habitats. Open stands of ponderosa pine and shrubs on dry, rocky surfaces were found to be important for maintaining CTF virus.