A retrospective review of the abdominal/pelvic ultrasound (US) examinations in 21 consecutive children with intussusception proven on barium enema was performed to determine what is the incidence of US detected peritoneal fluid in this population and to see if the rate of reduction was different in this subset. Twelve of the 21 children (57%) had free fluid demonstrated with US. Eight of these 12 (67%) had successful reduction. Six of the nine children (67%) without free fluid were also successfully reduced.