Only 15 families of decapod crustaceans living as larvae in oceanic waters of northern Chile survived the strong impact of the El Niño 1982-83 event. A key considering only their most conspicuous external characters, without specimens dissection, is given. These families represent one third of the total reported for the area living under "normal" oceanographic conditions; and at the level of species the 22 collected are almost one seventh of their total of 150. Species introduced in the area with more septentrional waters belong to the families Penaeidae and Sicyoniidae. Collected larvae were mainly those from intertidal and sublittoral waters