Ascites is the pathologic accumulation of fluid in the peritoneum. It is the most common complication of cirrhosis, with a prevalence of approximately 10%. Over a 10-year period, 50% of patients with previously compensated cirrhosis are expected to develop ascites. As a marker of hepatic decompensation, ascites is associated with a poor prognosis, with only a 56% survival 3 years after onset. In addition, morbidity is increased because of the risk of additional complications, such as spontaneous bacterial peritonitis and hepatorenal syndrome. Understanding the pathophysiology of ascites is essential for its proper management.