A comparative study of the breeding ecology of 12 raptor species was conducted in the eastern Great Basin from 1967-1970. The project was designed to determine the composition and densities, habitat selection, territoriality and predatory habits of raptorial birds in a semi-arid environment. All topics were analyzed comparatively, relating the requirements and activities of the 12 raptor species. Average yearly population densities of all species approximated 0.5 pairs per square mile. Predominant raptors were the Ferruginous Hawk and Great Horned Owl. The productivity of these and the other large raptors correlated closely with the abundance of their main food source, the Black-tailed Jackrabbit. The 12 species were able to coexist because of slight differences in their comparative ecologies. Those species most likely to be potential competitors differed significantly in their choice of nesting sites, activity periods, predation or nesting timetables. This area supports lower raptor populations than the eastern United States.