The purpose of this study was to determine rates of pneumonia and hospitalization for patients receiving oxygen therapy, patients having indwelling tracheostomy tubes, and those using tracheostomy or noninvasive methods of home mechanical ventilation. Six hundred eighty-four users of assisted ventilation for 13,751 patient-years or 19.8 years per patient were surveyed by mail and twice by telephone over a span of four years. Pneumonia and hospitalization rates were significantly higher for ventilator users with chronic obstructive pulmonary disease or with neuromuscular ventilatory insufficiency and gastrostomy tubes than for ventilator users with neuromuscular ventilatory insufficiency without gastrostomy tubes. Of the latter group, more than 90% of the pneumonias and hospitalizations were triggered by otherwise benign intercurrent upper respiratory tract infections. Oxygen therapy was associated with a significantly (P< 0.001) higher rate of pneumonias and hospitalizations than that seen for untreated patients after initial episodes of respiratory distress or during the use of either tracheostomy intermittent positive pressure ventilation or noninvasive ventilatory assistance methods. The lowest pneumonia and hospitalization rates (P< 0.001) were by full-time, noninvasive intermittent positive pressure ventilation users. We conclude that oxygen therapy is not an effective substitute for assisted ventilation for patients with primarily ventilatory insufficiency. Noninvasive ventilatory aids can be used effectively for up to full-time ventilatory support for patients with neuromuscular conditions whose bulbar muscle function is adequate to avert the need for gastrostomy tube placement.