Postoperative adhesions account for 64-79% of admissions with small bowel obstruction (SBO). The aim of this study was to identify the operative procedures and the types of adhesions that cause SBO. A retrospective analysis of all patients with an admission diagnosis of acute adhesive SBO between January 1982 and December 1990 was performed. One hundred and nineteen patients had 144 admissions with an initial diagnosis of acute SBO due to adhesions. The previous operations were: appendicectomy 23.3%; colorectal resection 20.8%; gynaecological surgery 11.7%; upper gastrointestinal (gastric, biliary or splenic) surgery 9.2%; small bowel surgery 8.3%; and more than one previous abdominal operation 23.6%. Sixty-one admissions required surgery to relieve the SBO. Eighteen patients had strangulated small bowel. All but two of these patients had a single band adhesion causing the SBO and associated strangulation. Band adhesions were commonly found following appendicectomy, colorectal resections or gynaecological operations. Seventeen of the 21 patients with previous surgery for a colorectal malignancy had benign adhesions causing the SBO, while four of the six patients with either previous ovarian or previous gastric carcinoma had recurrent malignancy causing the SBO. Five patients had previously undiagnosed carcinomas (three ovarian and two caecal) as the cause of the SBO.