By far, the most common causes of small bowel obstruction (SBO) are postoperative adhesions and hernias. Other less-common mechanical etiologies are bolus obstruction (e.g., bezoar), malignant or inflammatory (e.g., Crohn’s disease) causes, or intussusception. Hernias causing SBO are discussed in• Chap. 22; early postoperative small bowel obstruction (EPSBO) and paralytic ileus are discussed in • Chap. 48. SBO developing in the aftermath of bariatric abdominal surgery is discussed in • Chap. 31. Mention is made here of SBO in the virgin abdomen, intussusception, the cancer patient, radiation enteritis, and gallstone ileus. Peritoneal tuberculosis as a cause of SBO is mentioned in • Chap. 37.1. The bulk of this chapter is, however, devoted to adhesive SBO.