Clinical symptoms and gross autopsy findings in two cases of dieldrin poisoning are presented. Studies in one child suggest that redistribution of the insecticide into fat is slow and that the more rapid redistribution of dieldrin is from brain to muscle, which may account for termination of seizures. Concentrations fall to population levels with a first-order decay rate which had, in this case, a half-life of 50 days. Electroencephalograms, helpful for diagnosis, may reflect the brain load of poison. Evidence for liver toxicity was found both acutely and more than one year after poisoning.