Abnormalities in oesophageal, gastric and jejunal motility have been described in patients with chronic idiopathic constipation, suggesting that this may be a panenteric disorder. To test the hypothesis that ileal motility is also abnormal in constipation, terminal ileal motility was studied in ten patients and six healthy controls by prolonged and ambulant manometry. Mean(s.e.m.) phase II activity was significantly prolonged in patients compared with controls, during wakefulness (61.6(7.3) versus 19.3(3.5) per cent, P < 0.001) and sleep (44.4(9.0) versus 1.1(0.8) per cent, P < 0.001). The mean(s.e.m.) duration of phase III fronts was shorter in patients (7.9(1.8) min) than in controls (13.2(1.3) min; P < 0.001). Retrograde propagation was seen in approximately 15 per cent of all phase IIIs in patients but not in control subjects. The mean(s.e.m.) duration of postprandial activity was significantly shorter in patients than in controls (30.1(6.2) versus 130.0(68.0) min, P < 0.001). Ileal motility is abnormal in patients with chronic idiopathic constipation. This may result from an abnormality of the enteric nervous system or abnormal modulation of this system by the central nervous system.