The secretory behaviour of rat nasal glands, under normal conditions and after the application of cholinergic drugs, has been studied using morphological and radiobiochemical techniques. Autoradiography and electrophoresis provide evidence for the selective incorporation of 3H-arginine into the glycoprotein-containing fraction of the nasal glandular secretion. Radiobiochemical experiments show that labelled arginine is rapidly incorporated into the acinar cells of unstimulated glands, although it takes approximately 4 h before the labelled secretory proteins leave the cells. The secretion of proteins is stimulated by the parasympathetic agonist pilocarpine, whose main action is to promote discharge. Histological sections show a depletion of secretory granules after pilocarpine treatment. The cholinergic antagonist atropine inhibits the secretion; the acinar cells are completely filled with secretory granules following this treatment. The time course of the events following atropine administration suggests that there is no feed-back system controlling glycoprotein synthesis. The techniques employed here therefore appear to be useful for studying the effects of drugs that interfere with the secretory activity of the nasal glands.