Excretion of ammonia and inorganic phosphate and respiration of various size classes of Euphausia superba were studied in the Scotia Sea and in the north of the Weddell Sea. Freshly caught krill respired 0.63 ml O2g-1 dw h-1 and excreted 1.46 μg-at NH4-N and 1 μg-at PO4-P g-1 dw h-1. Carbon made up 45.4% and nitrogen 9.9% of body dry weight. During a starvation experiment over seven days respiration and ammonia excretion varied by a factor of two and did not reveal clear trends, whereas phosphate excretion decreased rapidly during the first day and remained constant afterwards at a low level. © 1983 Springer-Verlag.