Noninvasive PPV has been employed for decades in patients with chronic respiratory failure. Increasing use in patients with acute respiratory failure is a more recent phenomenon, mainly because of advances in noninvasive interfaces and ventilator modes. Noninvasive PPV delivered by nasal or oronasal mask has been demonstrated to reduce the need for endotracheal intubation, decrease lengths of stay in the ICU and hospital, and possibly reduce mortality. In the acute care setting, evidence now demonstrates the efficacy of noninvasive PPV for acute exacerbations of COPD, pulmonary edema, pulmonary contusions, and acute respiratory failure in patients who decline or who are not believed to be candidates for intubation. No firm conclusions can yet be made regarding patients with respiratory failure due to other causes, but studies suggest that noninvasive PPV may also be of benefit in patients with postoperative respiratory insufficiency, chest wall disease, and cystic fibrosis. Several factors are vital to the success of this therapy, including careful patient selection, properly timed intervention, a comfortable, well-fitting interface, patient coaching and encouragement, and careful monitoring. Noninvasive ventilation should be used as a way to avoid endotracheal intubation rather than as an alternative. Accordingly, a trial of noninvasive ventilation should be instituted in the course of acute respiratory failure before respiratory arrest is imminent, to provide ventilatory assistance while the factors responsible for the respiratory failure are aggressively treated. Moreover, the authors favor conservative management with expeditious intubation in patients who have other conditions that place them at risk during use of noninvasive ventilation or in patients failing to respond to noninvasive PPV. Noninvasive PPV clearly represents an important addition to the techniques available to manage patients with acute respiratory failure; however, because most studies have been retrospective and uncontrolled, many issues remain unresolved. Further controlled studies are needed to confirm the safety and efficacy of noninvasive PPV, evaluate the most appropriate selection of patients and timing of intervention, define the best type of interface, and assess the costs of noninvasive PPV in comparison with conventional therapy.