The temporal relationship of biliary motility to the duodenal migrating motor complex and effects of morphine and motilin were studied in five dogs prepared with a duodenal cannula. Common bile duct, sphincter of Oddi, and duodenal manometry were performed awake. Sphincter of Oddi phasic contractions occurred even during the quiescent period of duodenal phase I and its activity increased from phase II to III. Minimum basal pressure of sphincter of Oddi and common bile duct pressure decreased from phase I to phase III. Both morphine and motilin induced premature phase III in the sphincter of Oddi and duodenum. Latencies of the effect were 0.2 min for morphine and 3.2 min for motilin (P < 0.01). After morphine, vigorous continuous contractions with high basal pressure occurred, being interrupted by brief and repeated inactive periods, similar to spontaneous phase III. Motilin-induced phase III appeared indistinguishable from spontaneous phase III. Although both agents induced phase III in the sphincter of Oddi, differences in the latency and contraction pattern suggest different mechanisms of action of these agents on the sphincter of Oddi.