Eight hundred seventy patients were enrolled in a prospective study to identify risk factors for sternal wound complications following open-heart operations. The 0.8% incidence of major sternal complications was similar to that reported in the literature by other centers. The effects of age, sex, weight, operative time, type of procedure, resident versus attending surgeon, prolonged ventilatory support, reoperation for bleeding, external cardiac massage, and Dacron versus wire suture for sternal closure were assessed by stepwise logistic regression. Prolonged ventilation and female sex both strongly increased the risk of major sternal complications. Age and weight exerted lesser, but statistically significant, effects on the incidence of such complications. None of the other factors was associated with an increased risk of major sternal complications.