In a 52-year-old man who presented with an obstructive sleep apnea (OSAS) syndrome, we observed cerebral anoxic attacks during rapid eye movement (REM) sleep. Polysomnography showed that the attacks were due to severe hypoxia provoked by apneas lasting up to 220 s. Electroencephalogram (EEG) and clinical features clearly differentiate cerebral anoxic attacks from epileptic seizures. The length of apneas in our patient is very unusual, indicating an impairment of the mechanism terminating apneas. The cause of this impairment is unknown. However, this case report documents a possible pathogenetic mechanism other than heart arrhythmias responsible for sudden death or coma arising during sleep.