In order to investigate pathogenetic theories about the origins of biliary atresia, a model consisting of cell cultures of bile duct epithelium from the extrahepatic ducts of human and bovine origin is presented. The epithelial nature of the cultivated cells was documented by phase contrast microscopy, by electron microscopy and immunohistochemistry (anti-keratin). Inoculation studies of primary human cell cultures showed a cytopathic effect by light microscopy for all tested viruses (adeno, polio, herpes, rubella) except for reovirus type 3, for which a CPE was not demonstrable. A growth stimulating substrate for bile duct epithelial cells is described; among the purified growth factors epidermal growth factor was without effect (EGF), while cholecystokinin (CCK) led to an increase in cell numbers.