A tissue culture system for epithelial cells derived from human foetal pancreas has been established. The cultured cells show many ultrastructural features of interlobular duct cells. Immunocytochemical and histochemical evidence is presented in support of the view that these cells are ductal in origin. They are likely to be one of the few cell types that express the basic defect of cystic fibrosis in vitro. The cells may be passaged and sufficient material obtained to permit biochemical and molecular biological analysis.