Large-volume paracentesis is an accepted therapeutic modality for the treatment of tense ascites in patients with cirrhosis. Whereas the effects of large-volume paracentesis on the cardiovascular system have been studied in great detail, the effects of tense ascites and large-volume paracentesis on the respiratory system have undergone only limited evaluation. Most patients report symptomatic improvement in breathing after large-volume paracentesis. The aim of our study was to prospectively evaluate the effects of large-volume paracentesis on the pulmonary function of patients with tense ascites. Nine patients with alcoholic cirrhosis and tense ascites underwent large-volume paracentesis (mean, 3,500 ml of ascites removed) followed by intravenous albumin infusion (10 gm/L ascites removed). Pulmonary function tests were performed just before and 2 hr after large-volume paracentesis. The functional residual capacity increased from 2.46 ± 0.92 to 2.99 ± 0.97 L (p = 0.01) and total lung capacity from 5.08 ± 1.18 to 5.72 ± 1.32 L (p = 0.03). The forced vital capacity, expiratory reserve volume and residual volume also increased but were not statistically significant (p = 0.07 for all). We noted no significant improvement in forced expiratory volume in 1 sec, forced expiratory effort 25% to 75%, vital capacity or diffusion capacity. There was marked symptomatic improvement in all patients. We conclude that large-volume paracentesis improves measured lung volumes within hours in patients with tense ascites. (Hepatology 1994;20:825–828).