Endocrine cells have been observed from 13 cases of human fetal lungs through the using of Grimelius silver staining technique, fluorescence microscopy and ultrastructural examinations. They were found in great number in the small bronchi than in any other part of bronchial tree. Most of them were round or oval in shape, and usually rest on the basement membrane of epithelium. They were stained by Grimelius silver stain. After incubation with L-Dopa they emitted a green glyoxylic acid-induced fluorescence. Typical feature of these cells was the numerous electron dense neurosecretory-type granules, 168-312 nm in diameter, which can be seen throughout the cytoplasm.