Abdominal sonography as a noninvasive diagnostic method has proven to be of great value in evaluating patients with chronic inflammatory bowel diseases. The ultrasound pattern of bowel inflammation is characterized by a thickened and hypoechoic inflamed bowel wall, which appears like a target on transverse scans. Both Crohn's disease and ulcerative colitis can be detected with great sensitivity by abdominal ultrasonography. Ultrasonography (u.s.) reveals the intra- and extramural spread of the inflammation. U.s. is suitable method for the detection of abdominal complications, such as fistulas, abscesses and strictures, especially in patients with Crohn's disease. Duplex and color Doppler ultrasonography are helpful in the detection of the splanchnic hemodynamic changes in patients with intestinal inflammation. This offers a noninvasive and indirect means of assessing disease activity. Both endorectal ultrasonography and MRT are the most sensitive methods to detect fistulas and abscesses in patients with Crohn's disease. Because of the diagnostic possibilities, the unstressful nature of the procedure and the general acceptance by the patients, next to endoscopy, ultrasonography is the most important diagnostic procedure both as a primary diagnostic imaging modality and for the follow-up of patients with inflammatory bowel diseases.