Abstract. Zooplankton was sampled by a RectangularMidwater Trawl (RMT 1 + 8) in Weddell Sea surface waters (0 to 300 m) between 66 and 78°S during austral summer (February-March 1983). Sixty-nine taxa including different developmental stages were considered and divided into 16 size classes between < 1 and > 39.5 mm length. Biomass was determined by taxon and size class for three different meso-and macroplankton communities in the oceanic region, on the northeastern shelf and on the southern shelf of the Weddell Sea. The highest biomass of 11.2 mg DWm -3 (3.4 g DWm -2) was found in the northeastern shelf community (70 to 74°S), where juvenile and adult Euphausia crystallorophias accounted for 3 . 7 m g D W m -3 (1.1gDWm-2). Although not quantitatively sampled, early copepodite stages (CI to CIII) of Calanoides acutus and Calanus propinquus ranked second with 2.7 mg DWm -3 (0.8 g DWm-2). Biomass in the northeastern shelf community was concentrated in the size ranges 1 to 4 mm and 19.5 to 39.5 mm. The oceanic community of the central Weddell Sea was dominated by copepods smaller than 5 mm, which made up half of the total oceanic biomass. The tunicate Salpa thompsoni (7.0 to 8.5 mm) was the dominant single species with 1.6 mg DWm -3 (0.5 g D w m -a ) .Euphausiids, mainly juvenile and adult krill Euphausia superba, comprised 1.2 mg DWm -3 (0.4 g DWm-2).Total standing stock in the oceanic community was 9.4 mg DWm -3 (2.8 g DWm-2). Lowest biomass values were found in the southern shelf community (south of 75°S) with 4 . 0 m g D W m -3 ( l . 2 g D W m -2 ) , concentrated in the 1 to 4 mm and 14.5 to 34.5 mm size classes.Abundant species were the pteropod Limacina helicina

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