The loss of a substantial portion of a critically ill patient's inspired tidal volume through a bronchopleural fistula (BPF) may significantly alter the intra-pulmonary distribution of ventilation, ventilation-per-fusion matching and arterial blood gases. If surgical closure of the fistulous tract is not possible, modifications of traditional ventilatory methods may be necessary to preserve adequate gas exchange. The effect of the methods summarized later in this paper upon the patient's mortality and morbidity has not been rigorously analyzed in a large numbers of patients but has been presented in the case studies referenced. Although these techniques might be considered inves-tigational, they can be justified: (1) in the presence of profound hypoxemia and hypercarbia caused by a large BPF, and (2) when reduced gas loss through the fistula is considered an important part of therapy. All the methods discussed below apply in patients requiring endotracheal intubation and mechanical ventilation, whereas some (as indicated in the text) can be used during spontaneous breathing.