The causes of pneumomediastinum during perioperative period are trauma to the airway from intubation or other manipulation, raised airway pressure during anesthesia, rupture of a bleb or other intrapulmonary lesion, upper airway damage during neck surgery, infiltration of the tonsillar fossa or adenoid bed with air under pressure, increased airway pressure after nausea and vomiting, and coughing during awakening. This paper is represents and discusses a case of pneumomediastinum, pneumothorax, extensive subcutaneous and retroperitoneal emphysema which occurred suddenly a few minute after several times of bucking and straining in the intubated state with oxygen catheter after tonsillectomy and adenoidectomy at recovery room. The complieation was thought to be a infiltration of air through tonsillar fossa under pressure or alveolar rupture due to increased airway pressure after coughing. The patient was treated with high concentration of oxygen and recoverd uneventfully.