Pulmonary artery rupture is a rare complication of flow-directed catheters, which may lead to death due to uncontrolled hemorrhage. Between 1987-1994, pulmonary artery catheter have been inserted in 7200 cases who underwent open heart surgery. In 5 of these patients, pulmonary artery rupture associated with the use of flow-directed catheter was seen. Bleeding was thught to results from; the fragility of the arterial wall due to pulmonary hypertension in one patients, catheter migration during cardiopulmonary bypass (CPB) in there patients, and inadvertent use of the catheter in one patient. Conservative treatment mesures (tracheobronchial aspiration, irrigation with diluted adrenalin, PEEP and IPPV) were taken. Bleeding was controlled in the operation theater in 3 patients, and in one patient; it decreased slowly and stopped within 5 hours. The incidence of pulmonary artery rupture was found to be %0.07 in our center and male/female ratio was 4/1. There was no need for surgical intervention in any patient and mortality did not occur.