We present a case of 100% pneumothorax in a 41-yr-old man with a history of gastritis and gastroesophageal reflux scheduled for Nissen fundoplication. The patient was anaesthetized, and insufflation of the abdominal cavity with carbon dioxide was performed uneventfully. There was an increase in the peak inspiratory pressure and wheezing was noted with a decrease in the arterial oxygen saturation to 91%. An obstructive pattern was noted on the end tidal carbon dioxide monitor. The patient also had decreased breath sounds in the left lung field. The endotracheal tube was withdrawn 1.5 cm with equal breath sounds noted in both lung fields, but the wheezing persisted. At the end of the case the trocars were removed and the abdomen was deflated. The arterial oxygen saturation increased to 94% while breathing F1O2 of 1.0. A chest roentgenogram showed a 100% left pneumothorax. A left chest tube was placed with immediate improvement of the arterial oxygen saturation to 100%. We recommend monitoring of arterial oxygen saturation, peak inspiratory pressures, and excursion of the chest for early diagnosis and prompt treatment of pneumothorax during laparoscopic procedures.