Volvulus of the small intestine is a condition of bowel obstruction due to knotting and twisting of the small intestine. Two types of volvulus are described: 1) primary small intestinal volvulus where no predisposing factors exist, and 2) secondary volvulus where congenital or acquired conditions promote twisting of the small intestine. Over a 5-year period, 18 patients (eleven men and seven women) presenting volvulus of the small intestine are operated in the Emergency Surgery Clinic of the University Hospital "Queen Giovanna", representing 8.7 per cent of the total of 206 cases of small intestinal mechanical ileus (incarcerated herniations involving the small intestine are not included in the series). Primary volvulus is found in one patient. In those presenting secondary volvulus adhesions are the commonest underlying cause of small intestinal rotation--13 cases, next ranking primary tumor of the small intestine--one case, Meckel's diverticulum--one, carcinosis of peritoneum--one, and one patient with small intestine volvulation around colostomy. The most frequently encountered symptoms and laboratory examinations performed are analyzed. Intestinal necrosis is established in four instances (22 per cent). One patient dies of peritonitis and polyorganic insufficiency. Volvulus of the small intestine should be mandatorily considered in patients presenting mechanical ileus of the small intestine. Early operative intervention is a therapeutic approach contributing to preclude intestinal necrosis.