Heterotopic bone formation in abdominal scars is not as rare as the paucity of case reports in the literature would indicate. 2. Females comprised 21 percent of our patients. 3. The average age was fifty-five years. 4. The probable cause of this bone formation is injury to the xiphoid process above or the pubis below, with liberation of bone-forming cells into the wound. 5. Heterotopic bone usually remains permanently in the wound, but it can be absorbed and disappear, as was noted in one of our patients. 6. The bone should only be excised if it causes enough discomfort to warrant its removal. Careful removal should avoid recurrence. 7. In operations for intra-abdominal malignant lesions, bone formation should not be mistaken for recurrent malignant disease in the abdominal wall.
