Intravenous injection, in anesthetized rats, of a single dose of purified scorpion toxin (tityustoxin, TsTX), obtained from the venom of the Brazilian scorpion Tityus serrulatus, causes a striking increase in flow rate, protein content, kallikrein and amylase activities of the pancreatic juice. The flow rate and protein content of the juice remain significantly higher than in control rats, for at least one hour, whereas the kallikrein activity returns to control values 30 min after tityustoxin injection. Sub-diaphragmatic bilateral vagotomy does not prevent the pancreatic secretion induced by tityustoxin; moreover, vagotomy potentiates the flow rate and kallikrein secretion produced by the toxin. Pre-treatment of the rats with atropine blocks the pancreatic secretion evoked by tityustoxin. It is suggested that the pancreatic secretion induced by tityustoxin is due to actions of acetylcholine, released from postganglionic nerve fibers, on muscarinic receptors. The mechanism by which vagotomy potentiates the pancreatic secretion evoked by tityustoxin is under investigation.