Nontraumatic perforation of the small intestine is very rare in western countries, while typhoid fever is the most common cause of such perforation in other parts of the world. A series spanning 24 years is reviewed, comprising 112 adults with perforation of the small intestine resulting in peritonitis. Perforations due to Crohn's disease, strangulation, postoperative complications and malignancy are not included. Causes of perforation were ingested foreign body (24 cases), radiotherapy (18), potassium chloride medication (13), diverticula of the small bowel (10), Zollinger-Ellison syndrome (2), and tuberculosis, actinomycosis and intrauterine contraceptive device (each in 1 case). The etiology could only be suspected in 13 cases and in 31 it was unknown. Difficulties in making the preoperative diagnosis contributed to lateness of surgical intervention. Mortality (23%) was related to patient age and cause of the perforation. The series permitted no conclusions concerning relationship between surgical method and mortality rate, but it is recommended that the method be adapted from case to case, depending on the etiology of the perforation.