Intraluminal pressures were measured with four open ended, water perfused tubes in the fasting state and after a standard liquid meal (400 KCal, 375 ml, protein 15 g, carbohydrate 55 g, lipid 13.4 g) in six patients with sigmoid diverticular disease, 20 with the irritable bowel syndrome and in 13 controls. The pressure sensors were positioned in the true sigmoid colon at colonoscopy at 25, 35, 45, and 55 cm from the anus. Colonic pressures were significantly higher in diverticular disease than in controls before (p less than 0.02) and after the meal (p less than 0.002), some pressure amplitudes exceeding 300 cm H2O. Patients with the irritable bowel syndrome had lower (p less than 0.05) pressures than controls before the meal. Postprandial sigmoid pressures were within the mean +/- 2 SD of controls in 10, above in two and below in eight patients with the irritable bowel. Hypercontractility of the sigmoid colon in the irritable bowel syndrome was not confirmed under the conditions of this study. The association between sigmoid diverticulosis and high intraluminal pressures is confirmed.