A one year study was made of the carbon, nitrogen, phosphorus, and carbohydrate content of the major zooplankton groups from the surface to 500 m in the Sargasso Sea off Bermuda. Carbon content ranged from the yearly average of 41.6% of the dry weight of copepods to as low as 7.2% in the siphonophores. Nitrogen varied from approximately 9–11% of the dry weight of organisms with a low wet to dry weight ratio; 1–4% in the watery forms; and 6–8% in intermediate groups such as the chaetognaths. Average yearly phosphorus levels ranged from 1.48% of the dry weight in the euphausids‐mysids to 0.14% in siphonophores. Carbohydrate content of all groups was low, averaging less than 1% of the dry weight.