Although it is often functional at presentation, acute renal failure has a poor prognosis in patients with cirrhosis. The role of inflammation, a key event in the outcome of cirrhosis, has never been studied in this setting. We aimed to investigate the predictive factors of mortality in patients with cirrhosis and acute functional renal failure, specifically in relation to inflammatory events. One hundred consecutive patients with cirrhosis from 5 French hospitals were prospectively included at the day of onset of acute renal failure. Medical history, treatments, and procedures during the month before inclusion were recorded. Physical examination, blood and urinary chemistries, and renal ultrasound examination were performed. The presence of systemic inflammatory response syndrome (SIRS), infection, and sepsis was assessed. The primary outcome was in-hospital mortality. The mechanism of renal failure was functional in 83 patients. Causes of renal failure were hypovolemia (34%), hepatorenal syndrome without ongoing infection (17%), hepatorenal syndrome with ongoing infection (16%), nephrotoxicity (2%), and multifactorial (31%). SIRS was observed in 41% of patients, 56% of them with infection. In-hospital mortality was 68% in patients with SIRS and 33% in patients without (P = 0.001). In multivariate analysis, only model for end-stage liver disease score and presence of SIRS, but not infection, remained associated with a poor outcome. Conclusion: The presence of SIRS, with or without infection, is a major independent prognostic factor in patients with cirrhosis and acute functional renal failure. This suggests that preventing and treating SIRS could decrease mortality in patients with cirrhosis and acute renal failure. (HEPATOLOGY 2007.)