The improved study of the Eastern South Pacific undertaken in the last years enables us to have a better view of the marine communities' biogeography. The author, elaborating on several ideas of previous studies, proposes four subdivisions or districts in that region: 1) tropical of the Panamic-Pacific province up to 3º 30'S; 2) intermediate, from approximately 3º 30' to 7º S, where tropical and southern waters influence the presence of organisms; 3) temperate, of the Peruvian Coastal Current or Humboldt Current; and 4) tropical, in the waters off this last Current Joining the Peruvian Oceanic Current. The author, consulting extensive literature, examines the presence of molluscs and fishes, in order to select a characterization of each biogeographical district. Some of the proposals are, for instance, Littorina peruviana, Ocypode guadichaudii and Engraulis ringens for the temperate district; Littorina paytensis, Olivella broggi and Scorpaena afuerae for the intermediate one; the thunids and Exocoetus volitans for the tropical oceanic waters; and Anadara tuberculosa, Littorina varia, Pomadasys panamensis and Sciades troschelli for the tropical waters north of 3º 30'.
