Endrin is a fat soluble organochlorine insecticide. Commercial manufacture and use began in the early 1950s. It has been banned in most countries world wide during the last 25 years. Endrin is included in the Stockholm convention on persistent organic pollutants (POPs) and the United Nations Economic Commission for Europe (UNECE) Convention on long-range transboundary air pollution on POPs. Endrin is partly transformed in the environment into delta-ketoendrin. In both animals and humans, endrin is readily absorbed via the gastrointestinal tract. Compared to lower organisms which show some bioaccumulation, endrin is rapidly biotransformed in mammals and therefore does not bioaccumulate significantly. The dominant effects are neurotoxicity and liver toxicity, the latter seen following chronic exposure. Endrin is neither genotoxic nor teratogenic, but foetal toxicity can occur. Fish derived products, particularly fish oil, contained the highest levels of endrin. The majority of fish oil samples contained endrin at levels between 1 and 10 mu g/kg. Feed products of plant origin seldom show detectable levels of endrin. However, the limit of detection was often higher (1-10 mu g/kg) than that for fish oil. The levels found in feed are usually much lower than the levels which induce toxicity in farmed animals and pets. Due to the low production of endrin, its ban in the EU and most other countries world-wide and its rather low tendency to bioaccumulate in the environment, human daily intake for adults and children of this pesticide seems to be below 1 ng/kg b.w. Thus, human exposure is far below the provisional tolerable daily intake (PTDI) of 200 ng/kg b.w. established by JMPR (FAO/WHO Joint Meeting on Pesticide Residues).