Eighteen patients with acute and subacute Crohn's disease were examined by ultrasound. In 7, ultrasound was the initial screening procedure leading to the diagnosis of Crohn's disease. This diagnosis was subsequently proved by results of barium studies. The most frequent ultrasonographic finding was conglomeration: an irregular mass containing scattered echodense and sonolucent areas that represented matted inflamed bowel loops. Some of the conglomerations showed a fine diffuse echo pattern with ill-defined posterior borders due to poor transmission. These areas denoted mesenteric fat covering the matted loops (fatty conglomeration). Other ultrasonographic findings were the "target" or "bull's eye" sign, abscess formation, and fluid in the cul-de-sac.