The stomach accommodates to distension with a minimal rise in intragastric pressure, but the effects of gastric accommodation on overall gut motor activity are unknown. In four conscious fasted dogs, constant gastric distension (0, 10, 20, 40, 80, 160, 320, and 640 ml) was produced by an air-filled intragastric bag; intrabag and gastrointestinal pressure activities (fundus, antrum, and proximal intestine) were recorded for 4 h. With the bag empty (or without bag), the proximal stomach exhibited a fasting cyclic motor pattern synchronized with that in the antrum and upper intestine. During periods of activity the fundus generated powerful phasic pressure waves. Increasing intrabag volumes up to 80 ml gradually lengthened phase II of the intestinal interdigestive motor cycle. At 160 ml or more, gut cyclic motor activity disappeared and was replaced by continuous irregular activity, although the intrabag pressure increased to less than 7 mmHg. We concluded that gastric distension markedly alters gut motor activity even though gastric accommodation prevents a major increase in intragastric pressure.