DISCUSSION: Repeated Valsalva maneuvers are performed to increase the high during marijuana smoking. The elevated intrathoracic pressure leads to rupture of alveolar membrane causing positive pressure gradient of air from lungs into the mediastinum. In a retrospective study of 500 patients with mediastinal emphysema, 15 patients had repeated Valsalva maneuvers secondary to marijuana use. In all the cases, the patients recovered without further sequelae in two to five days. The differential diagnosis is broad and includes alveolar rupture, tracheobronchial injury, esophageal perforation, head/neck surgery and abdominal injury. Severe asthma, airway obstruction and rib fractures may lead to alveolar rupture. Iatrogenic injury and trauma to trachea, head, neck and abdomen often lead to tracking air down to the mediastinum, The most life threatening cause of pneumomediastinum is secondary to esophageal perforation. Tachycardia is the initial SIRS response within 24 to 48 hours. The Mackler's triad of vomiting, lower chest pain and subcutaneous emphysema may be present. Chest radiograph with water soluble material or a CT scan would be appropriate to identify perforation. Many patients need surgery as irrigation and debridement of mediastinum is required as well as closure of perforation. Percutaneous drainage is often a possibility if it perforation is in the neck and is easilly accessible.