Plankton samples were collected from 13 stations on the estuary of the river Paraíba do Norte (06º 56' to 07º 09'Lat. S). Copepoda were the most abundant holoplanktonic organism and from the meroplankton the larvae of Cirripedia were the best represented in the interior of the estuary. Gastropoda larvae occurred in almost all the stations being always more abundant than Lamellibranchiae ones, mostly near the mouth of the channel. Decapoda larvae and eggs and larvae of fishes were also frequent. The spatial and temporal distribution of zooplankton will be studied in the future.