Spontaneous bacterial peritonitis (SBP) represents a frequent and serious complication in patients with ascites in liver cirrhosis. Hospital mortality in patients with SBP reaches 10-20 %, so it is necessary to consider this diagnosis in every clinical decompensation of a cirrhotic patient, diagnose it early and treat it effectively. The clinical manifestation is nonspecific and variable, up to one third of patients might be asymptomatic. The diagnosis of SBP is based on the ascitic neutrophils count greater than 250 per mm3. Bacteriological examination of ascites fluid detects causative agents at less than half of the cases and the result is available after a few days. However, treatment should be initiated without delay. SBP is generally treated with antibiotics, the first choice therapy are the third generation cephalosporins, mostly cefotaxime, alternatively fluoroquinolones. Long-term prognosis of patients with the history of SBP is poor owing to its high recurrence rate, one-year survival after an episode of SBP is 30-40 %, 20 % at two years. Therefore, these patients should receive long-term antibiotic prophylaxis and should be evaluated for liver transplantation.