Superior cervical ganglion (SCG)-mediated effect of Pilocarpine (pilo.) on salivation of the rat submandibular gland was investigated. A total of 32 SD male rats, aged 12 weeks was divided into 4 experimental groups I to IV. They were anesthetized by pentobarbital (75 mg/kg, i.p.) and tracheotomized to allow artificial respiration. These rats were then ectomized only right SCG, leaving left SCG and injected with pilo. (8 mg./kg, i.v.). Rats of group I which were treated in the manner stated above were used as a control. Rats of group II and IV, of which adrenal glands were removed 18 hr before, were pithed 20 min before the injection of pilo. Rats of group III and IV were administered hexamethonium (C6) (1 mg/kg, i.v.). 5 min before the injection of pilo. Saliva from groups I to IV were collected separately from both salivary glands and flow rate of saliva were measured. Concentration of Na and K were also measured and total amounts of Na and K were calculated. 1) The flow rate induced by pilo. showed a tendency of increase in SCG-ectomized rats. 2) The flow rate showed also a tendency of increase in pithed rats. 3) The concentration and total amount of protein in saliva were decreased by SCG-ectomy. 4) The concentration of K was decreased in only SCG-ectomized rats whereas the total amount of K was closed in group I and II in spite of pithing and/or SCG ectomy. This reduction in K concentration seems to be caused by the increased flow rate as mentioned in paragraph 1). 5) SCG stimulating effect by pilo. was not antagonized, but rather activated by C6. 6) Submandibular ganglion-stimulating effect of pilo. was revealed in group III receiving C6, but this effect was extinguished in pithed rats of group IV. Considering of these results, it is proposed that SCG-stimulating ability of pilo., as shown previously by others, would be caused by activation of M1 receptor, which has sympathetic nerve stimulating effect on salivary glands, and may modify the salivation induced by stimulating effect of pilo. on M2 receptor. Moreover, results obtained with group III suggest that pilo. has submandibular ganglion-stimulating activity, although it's detailed mechanism is unknown.