This paper compares the effects on patients of perforation with barium and with air during attempted intussusception reduction by reviewing the clinical, radiological, surgical and pathological findings and sequelae in seven children who received barium and seven who received air. In both groups perforation occurred in infants under 6 months of age (with one exception) with a long duration of symptoms. All patients with barium enema required resection of bowel whereas only four with air enema required resection. Anesthetic times were longer in those patients with barium perforation in whom the intussusception did not move and there was a large leak. The patients with perforation due to air had a shorter hospital stay with decreased morbidity compared to those with perforation due to barium. Perforation occurred through areas of transmural necrosis in a minority of patients in each group. Perforations through normal bowel and shear injury (with air enema) indicate that increased pressure during the examination is an important factor in some patients. Because perforation with air is so much easier to deal with surgically and the children do better clinically, there is a tendency for some to consider perforation with air an inconsequential situation. However, a potential rare complication with this technique is tension pneumoperitoneum. Keeping this in mind, we continue to use air as the contrast of choice because the procedure in our hands is a safe, quicker and easier technique and we have achieved a substantial improvement in reduction rates. Overall reported perforation rates with air enema compare favourably with those due to barium enema.(ABSTRACT TRUNCATED AT 250 WORDS)