Two hundred and sixty-four cases of acute small bowel obstruction were retrospectively reviewed for the purpose of defining factors which could point to the presence of strangulated bowel. History, physical signs and investigations, including body temperature, X-rays, white blood count, and serum amylase, were not significantly different in the simple and strangulated groups. Although an elevated urinary white blood count and a palpable mass were more common in the strangulated group, they were not sufficiently reliable for early diagnosis of strangulation. In reviewing the literature, it is clear that all hernias with obstruction must undergo emergency surgery. Cases with intra-abdominal complete intestinal obstruction should also undergo emergency surgery. A more conservative attitude can only be taken when there is incomplete obstruction.