1. Pressure changes in the submaxillary and parotid ducts of dogs, induced by nerve stimulation or intravenous injection of drugs, were studied.2. Pressure rises could be elicited by parasympathetic stimulation and by acetylcholine and methacholine, even when no secretion was evoked. These effects were abolished by atropine.3. Similarly, sympathetic stimulation, adrenaline, noradrenaline and phenylephrine raised the pressure in both glands, also in the absence of secretion. Dihydroergotamine abolished these effects. Isoprenaline increased the pressure in the submaxillary duct, but only when it caused secretion. This effect was abolished by propranolol. In the parotid gland isoprenaline caused neither secretion nor pressure rise. It is concluded that the myoepithelial cells of the two glands are supplied with alpha-adrenoceptors.4. Doses of histamine, bradykinin, kallidin and physalaemin which caused no salivary secretion raised the duct pressure even when dihydroergotamine, propranolol and atropine had been given.5. Angiotensin and 5-hydroxytryptamine increased the pressure only in some experiments. Oxytocin caused very little or no pressure rise. Vasopressin had no effect of its own but reduced the pressure raising effects of nerve stimulation or drugs.