A panbiogeographic analysis of the distributional patterns of 196 species of eastern Pacific Isopoda led to the recognition of three generalized tracks, which correspond to major biotic components. The northern cold-temperate track extends from 62° to 35°N, in the northern cold-temperate sub-region (Aleutian Islands, Gulf of Alaska and coast of British Columbia, Washington, Oregon and northern California). The 57 endemic species assigned to it belong mainly to suborders Flabellifera, Valvifera and Asellota, although species of Oniscidea, Epicarida, Anthuridea, and Gnathiidea are also present. The northern warm-temperate/ tropical track extends from 33°N to 1°S, covering the Warm-Temperate and Tropical sub-regions, i.e., southern California to about halfway south into Ecuador. The 27 endemic species assigned to it belong mainly to the Flabellifera, most of them Cirolanidae and Cymothoidae, and Sphaeromatidae, Valvifera, Anthuridea, Asellota, Epicaridea, Oniscidea, and Gnathiidea are also present. The southern warm/cold-temperate track extends from 19° to 52°S, covering the Southern Warm and Cold-Temperate sub-regions, i.e., coast of Chile south to the Magellan Strait. The 27 endemic species assigned to it belong mostly to the Flabellifera, Asellota, and Valvifera.