The introduction of air into the venous or arterial circulation can cause cerebral air embolism, leading to severe neurological deficit or death. Air injected into the arterial circulation may have direct access to the cerebral circulation. A patent foramen ovale provides a right-to-left shunt for venous air to embolize to the cerebral arteries. The ability of the pulmonary vasculature to filter air may be exceeded by bolus injections of large amounts of air. Sixteen patients underwent hyperbaric oxygen therapy for cerebral air embolism. Neurological symptoms included focal motor deficit, changes in sensorium, and visual and sensory deficits. Eight patients (50%) had complete relief of symptoms as a result of hyperbaric treatment, five (31%) had partial relief, and three patients (19%) had no benefit, two of whom died. The treatment of cerebral air embolism with hyperbaric oxygen is based upon mechanical compression of air bubbles to a much smaller size and the delivery of high doses of oxygen to ischemic brain tissue.