Several groups of zooplankton from the coasts of California, British Columbia, and in the Arctic, including copepods, euphausiids, amphipods, crab zoea, ctenophores, and jellyfish rapidly took up 3H-benzpyrene, 14C-benzpyrene, 3H-methylcholanthrene, and 14Cnaphthalene from seawater solution. These hydrocarbons were metabolized to various hydroxylated and more polar metabolites by crustaceans but not by ctenophores or jellyfish. Up to 22 × 0−4 µg of benzpyrene was ingested by the temperate water copepod Calanus plumchrus, and transfer of this copepod to fresh seawater resulted in the discharge of most benzpyrene with less than 1 × 10−5 µg remaining after 17 days. When depuration was continued beyond 17 days, no further hydrocarbon loss was observed. Calanus hyperboreus from the Arctic took up to 11 × 10−4 µg of 3H-benzpyrene and a 28-day depuration experiment still showed the presence of benzpyrene in the copepod although again less than 1 × 10−5 µg.