We report a case of cerebral air embolism that occurred after chest trauma. The diagnosis was confirmed by CT and skull roentgenogram which demonstrated air bubbles in intracranial arteries. It is well recognized that cerebral air embolism is caused by various diagnostic and therapeutic procedures, and trauma. But it may often be overlooked because it is diagnosed clinically and there are no characteristic symptoms nor signs. Although various ways of treatment have been reported, prevention and early diagnosis are the most important. It is very rare that air bubbles are detected in skull roentgenograms in cases of cerebral air embolism. Only three other cases have been reported. One of these cases reported by Westcott awakens our interest because the patient died within only several minutes after the onset and underwent cardiac massage before the roentgenogram was taken, in the same way as our case. We think some artificial force is necessary to push air into intracranial arteries to the extent that it is detected on a skull roentgenogram. Little has been reported on CT findings in cerebral air embolism. Roughly speaking, three kinds of abnormal findings have been reported. They are air, edema, and infarction. In only nine cases including ours, air bubbles were detected on CT. In those cases CT scans were performed soon after the onset, twelve hours at the latest. Abnormal findings were detected in either bilateral hemispheres or in the right hemisphere only. Almost all lesions are located in the territory of the cortical branches, but in one case bilateral, thalamic infarction was noted, which is thought to be caused by embolism of thalamoperforators.(ABSTRACT TRUNCATED AT 250 WORDS)