The distribution of epidermal growth factor (EGF) and EGF receptor (EGFR) in adult human lung was examined by immunohistochemistry and immuno-electron microscopy. EGF immunoreactivity was observed in secretory granules and endoplasmic reticulum of serous acinar cells of bronchial glands. EGFR immunoreactivity was detected at the cell membrane of the basal cells and the bronchial surface nonciliated cells (indifferent cells) in the bronchus, the nonciliated bronchiolar cells (Clara cells) and the type II pneumocytes in peripheral lung. These results suggest that EGF is secreted into bronchial surface fluid from the bronchial glands and stimulates proliferation and/or differentiation of basal cells and indifferent cells of the bronchus, although the source of EGF responsive to Clara cells and the type II pneumocytes of peripheral lung was not determined.