Abst~act.Modem ~col.o_gical research often involves the comparison of the usage of habitat types or food Items to the availability of those resources to the animal. Widely used methods of determining preference from measureme~ts of usage and availability depend critically on the array of components that the researcher, often with a degree of arbitrariness, deems available to the animal. This paper proposes a new _metho~, base? on ranks of components by usage and by availability. A virtue of the rank procedure IS that .'t pro.vides co?II?arable results whether a questionable component is included or excluded from consideration. Statistical tests of significance are given for the method. . Th~ pape~ also offers a hierarchical ordering of selection processes. This hierarchy resolves certain mconsistencies among studies of selection and is compatible with the analytic technique offered in the paper.