Spontaneous pneumomediastinum is a rare, largely benign, self-limited disease. It is defined as the presence of air in the mediastinum without a precipitating event, such as penetrating trauma, infection, or esophageal rupture. Spontaneous pneumomediastinum generally refers to patients without underlying structural lung disease such as bronchiectasis, fibrosis, or emphysema. The proposed pathophysiology involves the development of an elevated pressure gradient between the alveolar space and the lung interstitium resulting in alveolar rupture. Air within the ruptured alveoli then dissects under the subpleural plane and decompresses into the soft tissues of the mediastinum, neck, and, rarely, the retroperitoneal space. Not surprisingly, activities that increase alveolar pressure, such as coughing, sneezing, vomiting, retching, exercise, inhalational drug use, and Valsalva maneuver during childbirth, have all been associated with the development of pneumomediastinum. However, in up to 50% of cases, no predisposing factor is identified.