The effects of galanin on gastric acid secretion and plasma levels of gastrin were studied in conscious dogs chronically fitted with gastric fistulas. Continuous i.v. infusion of galanin (2 micrograms.kg-1.h-1) for 2 h did not affect unstimulated total acid output or plasma levels of gastrin. In contrast, simultaneous i.v. infusion of galanin (1-2 micrograms.kg-1.h-1) inhibited the bombesin-stimulated output of acid whereas the effects of bombesin on gastrin output were not significantly modified. Galanin (2-4 micrograms.kg-1 i.v.) also depressed the secretory response to 2-deoxy-D-glucose without significantly affecting plasma gastrin levels. Galanin (2-4 micrograms.kg-1 i.v.) did not depress bethanechol-stimulated gastric acid output or inhibit histamine-stimulated gastric acid secretion. These findings indicate that glanin inhibits the bombesin- and 2-deoxy-D-glucose-stimulated secretion of gastric acid in conscious dogs by an action which is probably exerted at the level of the cholinergic nerve terminals.