Acute-on-chronic liver failure (ACLF) is defined as an abrupt deterioration of liver function in patients with established liver disease. Kidney function is almost universally altered in patients with ACLF due to underlying circulatory abnormalities. We review current advances during the past year in the diagnosis and management of renal failure in ACLF.The adequate measurement of renal function by means of clearance methods remains the gold standard for estimation of the glomerular filtration rate in patients with cirrhosis. The new definition of acute kidney injury needs to be specifically studied in patients with cirrhosis. Alternative kidney biomarkers of renal function in cirrhosis are promising and need further investigation. The most common cause of renal failure in cirrhosis is that associated with infections followed by hypovolemia-induced renal failure, intrinsic renal diseases, hepatorenal syndrome, and drug-induced renal failure. Adrenal insufficiency commonly occurs in patients with cirrhosis and hemodynamic instability. The proper diagnosis relies on corticotropin stimulation testing and the role of hydrocortisone therapy in these patients merits further investigation. Hyponatremia in cirrhosis is a major risk factor for the development of hepatic encephalopathy and is associated with a poor outcome in patients with ACLF and also after deceased donor and living-related liver transplantation. Vasoconstrictor drugs, particularly terlipressin, are effective for the management of hepatorenal syndrome. Predictive factors of response to terlipressin include serum bilirubin levels and the presence of an early increase in mean arterial pressure.The ongoing advances in the diagnosis and management of patients with ACLF and renal failure will improve the diagnosis, therapy and outcome of these patients.