We retrospectively reviewed the records of 18 children with acquired immunodeficiency syndrome (AIDS) who required mechanical ventilation for respiratory failure. These patients represented 35% of the patients seen with pulmonary disease and AIDS. The most common causes of respiratory failure were Pnuemocystis carinii pneumonia (77%) and bacterial pneumonia (33%). Bronchial lavage by fiberoptic bronchoscopy or endotracheal tube suctioning in mechanically ventilated children with AIDS had a high yield for P. carinii. Eight of 18 (44%) children survived the episode of respiratory failure and were weaned from the ventilator. However, four of eight survivors died within 6 months. Arterial oxygen tension on admission and maximum peak inspiratory pressure on the ventilator did not differ between survivors and nonsurvivors. We conclude that children with AIDS who are mechanically ventilated can be weaned from the respirator but that the subsequent course remains poor.