Thirty-two children with Crohn's disease were evaluated by real-time ultrasonography. The typical pattern of Crohn's disease caused by bowel wall thickening is the "bull's eye phenomenon", the elongated tubular stiff bowel loop with narrowing of the lumen and the small bowel conglomerate tumor. In indefinable abdominal complaints sonography may lead to the correct diagnosis. The differential diagnosis of similar sonographic features and the limitations of ultrasound in gastrointestinal disease must be considered. In proven Crohn's disease the findings in follow-up match the clinical course and may delineate complications, such as ileus, abscess, hydronephrosis, gallstones or involvement of parenchymal organs, as seen in 15 patients. Thus ultrasound will restrict repeated x-ray studies and support patient management.