Seven species of polychaetes are studied from benthonic samples collected by the Museu Riograndense de Ciências Naturais off the Barra do Rio Grande (Southern Brazil). Neanthes succinea, Marphysa sanguinea and Lumbrineris latreilli are considered cosmopolitan. Ophioglycera eximia was known only from the antarctic region. The area of distribution of Eunice rubra, known to go from the Gulf of Mexico and West Indies to the coast of Pernambuco, is now enlarged to South Brazil. Aglaurides fulgida has been identified with doubt because only a median fragment was obtained. The size of the fragment indicates an exceptionally large size for the whole worm. A new species is described Pherusa capitata sp. n.