A hepatic hydrothorax is a pleural effusion that develops in a patient with cirrhosis and portal hypertension in the absence of cardiopulmonary disease. The pleural effusion is derived from ascitic fluid that enters the chest because of the negative pressure within the pleural space via defects in the diaphragm. The peritoneal-to-pleural flow of fluid can be demonstrated by nuclear scanning, even when the ascites is not clinically apparent. The pleural fluid usually has the characteristics of a transudate. However, an occasional patient with hepatic hydrothorax will develop spontaneous bacterial pleuritis manifest by increased pleural fluid neutrophils or a positive bacterial culture and will require antibiotic therapy. Treatment of the hydrothorax is directed at the underlying liver disease but a dyspneic patient can obtain relief from a thoracentesis or paracentesis. When medical therapy fails, liver transplantation is the treatment of choice. Both transjugular intrahepatic portosystemic shunting and thoracoscopic repair of diaphragmatic defects with pleural sclerosis can provide symptomatic relief, but the morbidity and mortality of these procedures are high because of the fragile nature of the patients.