The case has been reviewed of a USAF pilot aged forty-five, who developed severe neurological signs and symptoms after flying a T-33 aircraft with a cabin altitude between 26,000 and 28,000 feet for approximately one hour and twenty-five minutes. He has retained residual weakness of the left upper and right lower extremity, memory and speech defects, and sensation alterations of the right face. The incidence of dysbarism, though still low, is increasing with fifteen in-flight episodes known to have occurred in the past two years. The etiology remains obscure except for an agreed role for evolved nitrogen. The treatment remains symptomatic, though compression to greater than one atmosphere has been tried on one case with encouraging results. It is considered undesirable to re-expose individuals having had severe dysbarism.