In the pig ileum galanin (GAL)-like immunoreactivity was identified in nerve cell bodies of the submucous plexus and in nerve fibers of the circular and longitudinal muscle layer. Infusion of 5.10(-10)-10(-8) M of GAL into the arterial line of the isolated perfused porcine ileum decreased the frequency of spontaneous phasic contractions in a dose-dependent manner. The frequency of phasic contractions during maximal inhibition by GAL 10(-8) M was 13 +/- 4% (mean +/- SE) of basal frequency (p less than 0.05). The recovery from inhibition by GAL 10(-8) M lasted 16 +/- 1 min. Tonic contractions were not observed in this experimental set-up, neither by standard perfused catheter manometry nor by measurement of cross-sectional area of an intraluminally located balloon. Infusion of GAL 10(-8) M decreased the venous release of vasoactive intestinal polypeptide to 80 +/- 8% of basal release (p less than 0.05). It is concluded that GAL may participate in the regulation of small intestinal motility in the pig.