Summary.The effects of prolonged treatment with pilocarpine and Hö 9980 on the activity of acetylcholine splitting enzymes and on the sensitivity to acetylcholine and adrenaline in normal and denervated salivary glands of the cat were studied. Hö 9980, piperidino‐aethyl‐diphenylazetamid hydrochloride, Hoechst, is a substance with an atropine‐like action. The submaxillary glands were preganglionically denervated and the parotid glands postganglionically denervated.A. Subcutaneous injections of pilocarpine twice a day for 8—12 days were found to produce the following effects:I. Submaxillary glands:Sensitivity.The supersensitivity to acetylcholine regularly found after denervation was prevented in the submaxillary gland; the secretory effect of acetylcholine after treatment was even less than on normal non‐treated glands.Enzymic activity.The difference in cholinesterase activity between a denervated and an innervated gland was abolished.II. Parotid glands:Sensitivity.The denervation supersensitivity to adrenaline and acetylcholine of the postganglionically denervated parotid gland was lessened or abolished.Enzymic activity.The pronounced difference in cholinesterase activity between a postganglionically denervated and a normal parotid gland was almost abolished.B. Subcutaneous injections of Hö 9980 once a day for two weeks were found to produce the following effects:I. Submaxillary glands:Sensitivity.The sensitivity of the normal submaxillary gland to adrenaline was increased to about the level reached after denervation (confirming Emmelinand Henriksson1953).Enzymic activity.The relation in cholinesterase activity between a normal and a denervated gland was not materially affected.II. Parotid glands:Sensitivity.The secretory effect of adrenaline on the normal parotid gland was equal, after treatment with the drug, to the secretory effect on the postganglionically denervated gland; the difference otherwise brought about by denervation being abolished.Enzymic activity.No effect on the cholinesterase activity neither in the denervated nor in the normally innervated parotid gland could be demonstrated; the marked fall in enzymic activity after postganglionic denervation could still be found.The findings are discussed in relation to the theory claiming enzyme decrease as the cause of supersensitivity after