We experienced a case of pathologic aerophagia in a 10-year-old girl who has mental retardation. It was observed that the abdomen was non-distended in the morning and became maximally distended in the evening. Increased passage of flatus, but normal eructation, was noted. Roentgenographic examination showed 'esophageal air sign', abnormal air shadow on proximal esophagus adjacent to the trachea, in simple chest X-ray and visible air swallowing fluoroscopically. We tried a percutaneous endoscopic gastrostomy (PEG) to decompress swallowed air in stomach. We suggest that placement of a PEG catheter in early life, especially in mentally retarded patients, that can be used as desufflator, can prevent the complications of aerophagia. 'Esophageal air sign' may be very helpful for early detection of pathologic aerophagia.