This study was designed to determine the role of the duodenum in controlling the interdigestive migrating motor complex of the canine stomach and small intestine. The motility patterns of 4 dogs were studied before and after resection of the entire duodenum with reimplantation of bile and pancreatic ducts. Before duodenectomy, plasma concentrations of motilin and pancreatic polypeptide varied cyclically with the migrating motor complex. After duodenectomy, the migrating motor complex was abolished in the stomach in 3 of the 4 dogs during fasting. The other dog demonstrated what appeared to be an intermittent cyclic increase in gastric contractile activity, but with markedly abnormal characteristics and at irregular intervals. The jejunal migrating motor complex continued to cycle after duodenectomy in all 4 dogs, but the mean period was shorter than before duodenectomy (83 min vs. 147 min, p less than 0.01). Duodenectomy abolished the cyclic variations of plasma motilin and pancreatic polypeptide and lowered the concentration of both peptides during all phases. This study suggests that the duodenum plays an important role in the initiation of the gastric migrating motor complex and in the coordination of interdigestive gastrointestinal motor activity, possibly by the release of motilin.