Acute kidney injury (AKI) is a common complication in critical illness that is associated with important acute and long-term morbidity and mortality. Patients at risk should be closely monitored since current diagnostic criteria may result in late recognition. Biomarkers of kidney injury can assist in earlier diagnosis. Although sepsis is the predominant cause of AKI in ICU patients, AKI may have several causes that must be differentiated and promptly acted upon to prevent further deterioration of kidney function. Optimisation of hemodynamics, early appropriate antibiotic therapy and avoidance of nephrotoxic substances are the most important preventive measures. Recent evidence suggests that AKI is an important risk factor for chronic kidney disease (CKD) and end-stage renal disease (ESRD).