Zooplankton samples were analysed for faunal composition, organic carbon, protein, carbohydrate and lipid content. Total zooplankton biomass (as displacement volume) varied from 0.032 to 0.500 ml.m sup(-3) (x = 0.23 + or - 0.14) in upper 200 m with significant difference between the Antarctic and the sub-Antarctic waters. Calanoid copepods were numerically the predominant group comprising greater than 80% of total counts, whereas, euphausiid Euphausia superba was abundant in samples collected south of lat. 55 degrees S. Organic carbon concentrations ranged from 0.83 to 13.04 mgC.m sup(-3) (x = 5.91 + or - 3.59). Lipid was the principal biochemical component, varying between 11.08 to 27.65% (x = 21.04 + or - 4.39). Protein content showed large variations and ranged between 8.02 and 29.9% (x = 19.57 + or - 6.25). Values for carbohydrate content varied from 11.01 to 27.65% (x = 19.62 + or - 4.80). Higher accumulation of lipids in Antarctic zooplankton during phytoplankton blooms (austral summer) could be an adaptative phenomenon, and may function as metabolic reserve and insulation layer