Twenty-eight patients with inflammatory bowel disease were examined with ultrasound. When possible, maximum bowel wall thickness was measured and the site of any focal abnormality recorded. There were 19 patients with Crohn's disease and nine with ulcerative colitis. Bowel wall thickness ranged from 0.5-1.8 mm in the Crohn's group to 0.3-0.8 cm in the ulcerative colitis group. Following treatment, a measurable reduction in bowel wall thickness was demonstrated in 13 of the patients with Crohn's disease. No significant change in bowel wall thickness was detected in five of the patients with ulcerative colitis. The results echo the findings at double-contrast radiography and suggest a possible role for ultrasound in the assessment and follow-up of inflammatory bowel disease.