Ponderal index as a predictor of postoperative complications. Four hundred sixty-eight patients undergoing elective surgery were prospectively followed for the development of postoperative complications. There was a trend toward increasing complication rate with a lower ponderal index. However, lower ponderal indices were associated with increasing rates of diabetes mellitus and hypertension. Of these patients, forty cases with postoperative complications were matched to 40 control cases for sex, age, concomitant illness and operation performed. The cases of postoperative complications had a statistically significantly lower ponderal index than the controls (11.98 versus 12.43). The increased risk of postoperative complications in those patients with a ponderal index of less than 11 was 3.36, and less than 13 was 3.44. Surgeons who treated patients with lower ponderal indices need to have a high index of suspicion for the development of postoperative complications in these patients. 