Pneumocystis carinii pneumonia (PCP) causing acute respiratory failure (ARF) in patients with acquired immunodeficiency syndrome (AIDS) has been reported in several studies to have a mortality of 84 to 100 percent. A recent report found a 42 percent survival rate. We followed 58 patients with AIDS who required positive pressure ventilation and identified 33 patients with PCP and ARF who had a PaO2/FIo2 level less than 150 mmHg. We report the survival of 12 of these 33 (36 percent). The mean duration of survival after discharge from the hospital was 7.9 +/- 1.8 months, which is an improvement over previous reports. These data suggest that we should reevaluate the reported recommendations that patients with AIDS, PCP and ARF should not receive intensive care or mechanical ventilation.