Hepatic hydrothorax is an important and difficult-to-manage complication of cirrhosis and portal hypertension. Here, we aimed to study its clinical features and natural history. Complete clinical data, including outcomes, were abstracted from hospital records of patients with cirrhosis and ascites admitted to University of Texas Southwestern University teaching hospitals from January 2001 to July 2012. Hepatic hydrothorax was diagnosed based on currently accepted clinical characteristics of the disease, including a known diagnosis of cirrhosis, the presence of portal hypertension, pleural fluid analysis, and the absence of primary cardiopulmonary disease.Seventy-seven of 495 (16%) hospitalized cirrhotic patients with pleural effusion (28 female; mean age, 52 yr) met the criteria for diagnosis of hepatic hydrothorax. Resting dyspnea and cough were the most prominent presenting symptoms, occurring in 34% and 22% of patients, respectively. Pleural effusions were most often right-sided (56/77; 73%), followed by left-sided only (13/77; 17%) and bilateral effusions (8/77; 10%); 7 (9%) patients did not have detectable ascites. The mean Model for End-Stage Liver Disease (MELD) score at presentation was 16. The serum to pleural fluid albumin gradient (SPAG) was ≥1.1 in all 48 patients in whom it was measured. Most patients (64/77; 83%) were managed with diuretics and/or thoracentesis, while 8 (10%) underwent transjugular intrahepatic portosystemic shunt (TIPS) and 5 (7%) underwent liver transplant. A total of 44 of 77 (57%) patients died during a mean follow-up of 12 months. The average time from presentation to death for all patients was 368 days, while for those after TIPS it was 845 days. No deaths were reported in the liver transplant group. The data indicate that a substantial number of patients with hepatic hydrothorax had what may be considered atypical presentations, including left-sided only effusions, or pleural effusion without ascites. Here, we propose that the term "serum to pleural fluid albumin gradient (SPAG)" be used to describe the gradient between serum and pleural fluid albumin levels and suggest that not only is it consistent with the portal hypertensive pathophysiology of hepatic hydrothorax, but also it is a useful criterion for diagnosis of hepatic hydrothorax. Finally, the overall outcome of hepatic hydrothorax was extremely poor, except in those undergoing TIPS or liver transplantation.