Air embolism to the brain is an accident that may occur in situations that favour the entrance of air into the bloodstream. The clinical diagnosis is sometimes difficult and only the computerized axial tomography may be of invaluable help. We present a rare case of air embolism occurring during sleep in which no apparent causes could be established. This woman had clinical findings of extensive infarction at the right cerebral hemisphere. The axial tomography performed during the first five days showed the presence of air bubbles persisting for three days and areas of infarction and edema during the 3rd-5th day. Magnetic resonance evidenced new areas of infarction in both hemispheres by the 12th day. Application of antiedema therapy was followed by a partial clinical recovery.