In a study of 47 aviator patients consecutively referred to U.S. Air Force School of Aerospace Medicine for evaluation of alteration of consciousness, 34 cases of syncope were identified. Mechanisms of etiology included 24 with vasovagal syncope, 4 with micturition syncope, and 6 with miscellaneous causes. Each diagnostic group was separately compared to a group of 26 control (nonsyncopal) patients. Clinical findings of the different diagnostic groups are presented. Notable differences in antecedent factors, clinical findings, and consequences of syncope are discussed.