This study examined the hypothesis that small bowel obstruction in patients whose only previous laparotomy was for appendicectomy or operation on the ovary or tube is unlikely to resolve with non-operative management. Results of 330 admissions for small bowel obstruction were examined. In 40 cases the only previous laparotomy was at appendicectomy or tubo-ovarian operation; in 38 (95 per cent) of these division of adhesions was undertaken compared with 154 (53 per cent) of the remaining 290 (P < 0·00001). In the former group band adhesions were commoner (86 versus 45 per cent, P < 0·00001), bowel resection was required more frequently (22 versus 10 per cent, P = 0.02) and it was considered safe to give a trial of non–operative management less often (60 versus 85 per cent, P = 0·0004). A trial of conservative management may be unsafe or not worth while in patients with obstruction following earlier appendicectomy or operation on the ovary or tube.