BACKGROUND renal insufficiency (RI) is a frequent complication in patients with cirrhosis and ascites. OBJECTIVE to assess the incidence, causes, predictive factors and prognosis of RI in cirrhotic patients with ascites. METHODS descriptive study of cases and controls. Clinical histories of 162 admissions in 103 patients during 3 years were reviewed. It was considered RI when there was an increase of creatininemia > 1.5 mg/dl. The predictive factors, clinical features, and mortality of the patients with and without RI were compared. RESULTS a diagnosis of RI was made in 35 cases (21.6%). Hospital mortality rate was 18.5%: with RI 57.1%, controls 7.8% (p<0.01). BACKGROUND reversible prerrenal failure (54.3%), SHR 1 (14.2%) and 2 (5.7%), septic shock by spontaneous bacterial peritonitis (SBP) (11.4%), NTA (8.5%). The patients with and without RI had a Child-Pügh score average (+/-DS): 12.8 (1.8) and 11.4 (1.9) (p=0.0002) respectively. The patients with RI had higher values of total bilirubin, AST, ALT, white blood cells, time prothrombin, and minors values of serum sodium, Hto, Hb, protein, albumin and cholinesterase that controls (p<0.05). The clinical variables associated with RI included infections (OR 1.4), SBP (OR 4) and hepatic encephalopathy (OR 2.4). In the multivariate analysis, the independent predictive factors for RI were hyponatremia, bilirubinemia greater to 10 mg/dl and SPB. CONCLUSIONS in cirrhotic patients RI have high mortality. The most frequent cause was reversible prerrenal failure. The risk of RI was increased significantly in patients with hyponatremia, marked hyperbilirubinemia and SPB.