Between January 1980 and December 1990, 75 (57.3%) of 131 patients with metastatic gestational trophoblastic tumor had pulmonary metastases detected on plain chest roentgenography at the King Faisal Specialist Hospital and Research Centre. Pulmonary involvement was commonly extensive, with 32 (42.7%) patients having > 10 pulmonary metastases and 45 (60%) patients having a pulmonary lesion > 5 cm in diameter. Greater than 50% lung opacification, mediastinal involvement and pleural effusion were present in 25 (33.3%), 25 (33.3%) and 36 (48%) patients, respectively. Eight (10.7%) patients developed early respiratory failure requiring mechanical ventilation within one month of presentation. The development of early respiratory failure was significantly associated with the presence of dyspnea, anemia, clinical pulmonary hypertension, cyanosis, > 50% lung opacification, mediastinal involvement and bilateral pleural effusion. Because all patients requiring mechanical ventilation died, the use of extracorporeal perfusion should be considered in patients with early respiratory failure.