BACKGROUND/AIMS: Liver cirrhosis and malignant tumors are two major causes of ascites according to the reports from Western countries, 80% and 10% respectively. Assuming that there might be regional differences in etiologies and changes in their frequency over time, we investigated causes of ascites and the diagnostic usefulness of various laboratory tests. METHODS: Medical records of 366 patients, who underwent diagnostic paracentesis in the mid-1990s (1996 and 1997) and early 2000s (2001 and 2002), were retrospectively reviewed. The etiology was confirmed by histology, imaging studies, and ascites analyses. RESULTS: The frequency of cirrhotic ascites was 59.6%, cancer-related 25.7%, tuberculous peritonitis 6.6%, and others 8.1%. Among cirrhotics, the frequency of cases related to hepatitis B decreased significantly from 72% to 55% over time, and alcoholic cirrhosis increased from 18% to 34%. Among cancer-related ascites, peritoneal carcinomatosis type was 75.5% (primary sites: stomach 24.5%, pancreas 15.9%, colon 15.9%, lung 7.4%, etc), metastatic liver cancers 8.5%, hepatocellular carcinoma without cirrhosis 6.4%, etc. The sensitivity of serum-ascites albumin gradient for the diagnosis of cirrhotic ascites was 91.4%, and total protein in ascites also revealed a comparable diagnostic sensitivity, 90%. The diagnostic sensitivity of adenosine deaminase for tuberculous peritonitis was 94.2%, and its positive predictive value was 75%. CONCLUSIONS: Liver cirrhosis is the leading cause of ascites, especially alcoholic cirrhosis has significantly increased. The next common etiology is cancer-related, and its frequency in Korea is higher than in western countries. Tuberculous peritonitis is still prevalent, and adenosine deaminase could precisely differentiate it from other causes.