Transabdominal ultrasonography is a noninvasive, radiation-free method that is well tolerated by patients with acute abdominal symptoms. The aim of this study was to investigate the validity of transabdominal ultrasonography, compared with plain abdominal film and small bowel enteroclysis, in the diagnosis of small bowel obstruction in patients with Crohn's disease (CD). Forty-four patients with CD ileitis or ileocolitis and acute obstructive symptoms who received ultrasonography and plain abdominal film at hospital admission were evaluated by small bowel enema before dismissal or surgery and were considered for statistical analysis. Small bowel obstruction was diagnosed by ultrasonography in 23 of 44 patients (52%), by plain abdominal film in 26 of 44 patients (59%), and by small bowel enema in 28 of 44 patients (64%); the diagnostic accuracy of plain abdominal film and ultrasonography compared with small bowel enema was 73% and 89%, respectively. Ultrasonography proved to be highly specific (100%) with no false positive results. Surgery performed in 25 of 44 patients for symptoms refractory to medical treatment confirmed the high diagnostic value of ultrasonography. The result of this study indicates that transabdominal ultrasonography is accurate and highly specific in the diagnosis of small bowel obstruction and can be considered a valuable first choice examination in CD patients with obstructive symptoms.