The benthic macroinvertebrate assemblages of the Argentine continental shelf were studied from samples of molluscs, echinoderms and bryozoans collected by the RN Shinkai Maru. Two major faunal groups were distinguished: one inhabiting the warmer inner shelf off Buenos Aires and northern Patagonia, and the other occupying the colder middle and outer shelf off Buenos Aires and most of the Patagonian shelf. These results confirm the traditional biogeographic division of the Argentine continental shelf into two provinces: Argentine and Magellanic. Furthermore, the results suggest the possibility of subdividing the Atlantic sector of the Magellanic province into two districts: Patagonian and Malvinean, under the influence of the Patagonian and the Malvinas current, respectively.