Twelve human near-drowning victims were treated, and their clinical courses were studied with particular attention given to electrolyte and blood gas changes. Ten of these patients made complete uneventful recoveries. The primary pathophysiological disturbance which necessitated emergency therapy was acute asphyxia with persistent arterial hypoxemia and acidosis. Initially the hypoxia appeared to be due to perfusion of nonventilated alveoli. Persistent arterial hypoxemia was present, however, even after a significant intrapulmonary shunt could no longer be demonstrated. The plan of management for each patient should be determined by individual laboratory and clinical studies.