The measurement of static pulmonary compliance by means of pressure-volume curves is an useful tool in the management of patients with acute respiratory failure. On admission to our Intensive Care Unit, we calculated the static pulmonary compliance values from the pressure-volume curve in 55 severe acute respiratory failure patients under mechanical ventilation. A predictive model, based on static pulmonary compliance measured on the deflation of the pressure-volume curve and patients' age, was developed using a function derived by stepwise discriminant analysis. Thirty-six of the 40 patients (90%) in the learning sample and 12 of the 15 patients (80%) in the test sample were correctly classified into survivors or non-survivors. The overall classification demonstrated an accuracy of 88% (48 of 55 patients). We conclude that the value of static pulmonary compliance can be an useful prognostic factor in patients with severe acute respiratory failure.