Heterotopic bone formation has been previously noted in abdominal laparotomy scars, but the presence of ectopic bone within the peritoneum is extremely rare. Our patient had recurrent formation of heterotopic bone involving the abdominal wall, peritoneum, and small-bowel mesentery. The features of various types of ectopic calcification are discussed, and several theories concerning the pathogenesis and treatment of heterotopic ossification are examined.