A 11-year-old, 19.40-kg, female Australian Sheppard was admitted for difficulty in sleeping due to persistent panting in summer. She could sleep once she was cooled by winds. This sign had been evident for the last three years. On admission, she had no stridor. Arterial blood gas analysis showed acute hyperventilation (Paco2 21 mmHg). CBC and biochemistory profile, skull and chest X-rays, and fluoroscopy revealed unremarkable. Laryngoscopy via LMA under light plane of general anesthesia by administering thiopental 5mg/kg IV revealed that regular constriction of rima glottidis on expiration, abduction of arytenoid cartilage. Anterior rhinoscopy disclosed no obstructive lesions. Tracheobronchoscopy via LMA revealed unremarkable, including BALF cytology. The dog was diagnosed with abnormal laryngeal movement. The pathophysiology remains to be unclear at this time. “Dynamic laryngeal narrowing on expiration “ was called for the time being, such as #459. It is considered that persistent panting occurred from hyperthermia, which derived from such a obstructive laryngeal disease. She was tried to be prescribed with nebulizer therapy including bronchodilator drugs to relax the intrinsic laryngeal muscles, though it is not unknown to be effective.