Here we want to call laparoscopist's attention to pneumothorax after diagnostic laparoscopy. Diagnostic laparoscopy has less complications, compared with laparoscopic surgery. In our experience, only one case (0.04%) developed pneumothorax during routine diagnostic laparoscopic procedure. This complication is presented in a 50-year-old female. She complained of dyspnea just after the decrease of intraabdominal pressure and deflation of intraperitoneal gas. The chest roentgenogram showed a right pneumothorax, and a right chest tube was inserted with immediate relief of tension. Pneumothorax during diagnostic laparoscopy is relatively rare but a major complication; Medline literature research showed six reported cases of pneumothorax after diagnostic laparoscopy from 1983 to 1998 including our case. The etiology was idiopathy in 5 and diaphragmatic injury in 1. Hypotension, elevation of inspiratory pressure, dyspnea, a decrease in systemic oxygen saturation, and loss of breath sounds suggest tension pneumothorax. The clinical condition of the patients improved rapidly because of the easy diffusion of the gas used in laparoscopy. Diagnostic laparoscopists should be aware of this complication and treat ventilatory problems.