Small bowel obstruction, excluding postoperative adhesive ileus, in patients > 1 month old treated between June 1982 and May 1992 at Gunma Children's Hospital Medical Center is reviewed. There were 32 patients, 22 boys and 10 girls, whose ages ranged from 1 month to 6 years (median 9 months). Intussusception was the most frequent cause of obstruction and was seen in 17 patients (53.1%). Causative lesions were identified in five patients, and were ileal duplication cysts in four and Meckel's diverticulum in one. Incarcerated inguinal hernia and mesenteric cysts resulted in bowel obstruction in six and three patients, respectively. Other causes included mesodiverticular band, ileal volvulus without malrotation, abnormal adhesion of omentum, abnormal band, vitelline duct remnant and trapping in a mesenteric defect. As for the age distribution, there was no significant correlation between the causes of obstruction and the age of patients. Ultrasonography was useful in differential diagnosis, and this modality should therefore be used in every patient with signs of small bowel obstruction.