Lipophilic sediment extract originating from the Kafue River, Zambia, was evaluated for toxic potency. Two different bioassays were used. In the first, sediment extracts were injected into newly hatched rainbow trout yolk-sac fry, and in the second chick embryo livers were incubated in vitro in different concentrations of the sediment extract. A dose-dependent ethoxyresofurin-O-deethylase (EROD) induction was recorded in both experiments. Furthermore, various types of intracellular alterations characterized by degenerative and necrotic changes were observed in the hepatocytes of the exposed groups. These findings indicate the presence of EROD inducing dioxin-like lipophilic substances in sediment extracts originating from the Kafue River near the town of Kitwe.