Autonomic nerve function was evaluated in 40 patients with total ulcerative colitis and in 25 patients with irritable bowel syndrome by three established non-invasive tests based on the heart reactions to deep breathing (E/I ratio) and tilt (acceleration and brake index). None of the patients were diabetic. Most of the patients with ulcerative colitis were clinically and biochemically inactive; 10 had previously undergone colectomy. The results were compared with a control group consisting of 56 healthy individuals and 33 previously investigated patients with Crohn's disease, 45% of whom demonstrated autonomic neuropathy (AN). Patients with ulcerative colitis had a significantly lower E/I ratio than controls in age-corrected values, indicating vagal nerve dysfunction. Altogether, 35% had signs of AN. In patients with irritable bowel syndrome 36% had evidence of AN, a figure in agreement with observations from other investigators. We conclude that AN is common in patients with ulcerative colitis, regardless of disease activity and previous colectomy. In contrast to a predominantly sympathetic dysfunction in Crohn's disease, AN in ulcerative colitis was vagal.