1. The incorporation of tritiated glucose into bronchial gland cells enables their glycoprotein secretion to be followed by radioautography. The number of cells from which secretion is observed after 4 h of cell culture is the secretory index.
2. Large variations in secretory index were observed between the bronchi of different subjects, but the secretory index was proportional to gland size.
3. The secretory index was increased by parasympathomimetic drugs and diminished by parasympatholytic drugs, the magnitude of the effect being proportional to gland size in the former and inversely proportional in the latter case.
4. Sympathomimetic drugs, bradykinin and mucolytic drugs had no effect on the secretory index.
5. In cystic fibrosis, bronchitis and bronchiectasis gland size and not the disease process was the main determinant of the secretory index.