The spatial distribution of copepod populations on the eastern continental shelf off Rio de Janeiro State, Brazil, was analysed in relation to the hydrographic regime in December-January (summer 1991/92) and July (winter 1992). Advection of cold and nutrient-rich South Atlantic Central Water (SACW) onto the shelf was a prevailing circulation mechanism in both seasonal cruises. The SACW occupied a larger proportion of bottom layers in summer as compared to winter, but only in the latter a well-defined upwelling event was recorded off Cape Frio. Two calanoid copepods were representative of shelf areas influenced bySACW intrusions: Calanoides carinatus, which occurred mainly during summer and Ctenocalanus vanus, recorded at high densities in both periods. Paracalanus quasimodo was the dominant copepod at inner- and mid-shelf stations both in summer and winter, followed by Temora spp. and Oncaea spp. These coastal species peaked at the upwelling site. A highly diversified and comparatively less abundant copepod assemblage, dominated by Clausocalanus furcatus and Oithona plumifera, was recorded in outer-shelf stations occupied by the oligotrophic Tropical Waters of the Brazil Current. We conclude that regional and seasonal contrasts in copepod species composition and abundance are controlled to a great extent by the advection and upwelling of the SACW onto the shelf. [ABSTRACT FROM AUTHOR]