To investigate effects of intraduodenal air insufflation on sphincter of Oddi motility, manometric recordings were obtained during fasting from the sphincter and duodenum in four conscious dogs with duodenal cannula. At 40% of the mean cycle length of the migrating motor complex predetermined from baseline recording, 160 ml of air was injected into the duodenum. In both the sphincter and duodenum, air insufflation produced premature phase III-like activity in seven of 20 experiments (35%) or nonspecific excitatory reaction in eight (40%). In the remaining five experiments (25%), the sphincter exhibited a transient inhibitory response, while the duodenum showed the nonspecific excitatory reaction. Basal pressure of the sphincter increased immediately after air insufflation in 90% of the 20 experiments. The mean basal pressure increased from 12.3 +/- 1.6 mm Hg to 22.4 +/- 2.1 mm Hg (P < 0.0001) and minimum basal pressure from 2.9 +/- 0.9 mm Hg to 4.7 +/- 0.8 mm Hg (P < 0.001). These results indicate that intraduodenal air insufflation does affect motility of the sphincter of Oddi and duodenum in conscious dogs.