To study effects of intrasphincteric injections of botulinum toxin on the sphincter of Oddi cyclic motility and responses to motilin and cholecystokinin, four conscious dogs with duodenal cannula underwent manometry of the common bile duct, sphincter of Oddi, and duodenum. After baseline recording, each dog had intrasphincteric injections of saline or botulinum toxin. The injections of saline had no effect, whereas botulinum toxin significantly reduced mean basal pressure, amplitude, and motility index of the sphincter of Oddi. These effects took place in four to seven days and reached a maximum in seven to 10 days. The basal pressure returned to the baseline level in 28 weeks, but the amplitude and motility index remained low. The pressure parameters of motilin-induced premature phase III-like activity also decreased, but action of cholecystokinin was not affected. These results indicate that the botulinum toxin injections reduce sphincter of Oddi phasic contractile activity for a prolonged period of time.