A great number of studies using Heidenhain pouches have been reported, but most of them have been concerned with secretory activity. Studies on the motor activity of the pouch are few, and our knowledge about it is rather limited. In the present study, therefore, long-term changes in contractile activity of the Heidenhain pouches were recorded simultaneously with those of the main stomach in conscious dogs by means of chronically implanted force transducers. It was found that during the interdigestive state Heidenhain pouches contracted precisely in association with the main stomach. During this time a series of strong contractions arose simultaneously in the Heidenhain pouch and the main stomach, lasted for 24.2 +/- 1.90 min, and then ceased abruptly. Such strong contractions were followed by a long period of motor quiescence lasting for 86.9 +/- 6.06 min. These characteristic recurring episodes in the Heidenhain pouch and the main stomach lasted during the interdigestive state but were inhibited by the ingestion of food or intravenous administration of pentagastrin. These findings indicate that the interdigestive motor activity of the stomach is strongly controlled by a humoral factor(s) rather than the parasympathetic nervous system; however, we also propose a possible role for the sympathetic nervous system for coordinated occurrence of the interdigestive contractions between the Heidenhain pouch and the main stomach.