Pulmonary edema after re-expansion of a pneumothorax occurs within a maximum of 3 days of the pneumothorax and manifests by intense clinical signs (cough, abundant foamy expectoration, major cyanosis), marked hypoxia and a "white lung" radiologic image. The outcome was rapidly favorable in the case reported, despite the severity of the initial symptomatology. Currently accepted physiopathologic mechanisms implicate numerous factors in the genesis of edema due to re-expansion. The lesional pulmonary edema can be explained by alteration in alveolar capillary permeability, by the atelectasis, hypoperfusion and stretching during revascularization, and possibly by the action of free radicals. A hemodynamic edema also exists as a consequence of the reduction in pulmonary interstitial pressure. Possible prophylactic measures are discussed, the most appropriate appearing to be very progressive evacuation of the pneumothorax.