Acute kidney injury (AKI) is a common and serious complication in critically ill patients. The mortality rate remains high despite improved renal replacement techniques. A possible cause of the high mortality rate is that intensive care unit patients tend to be older and more debilitated. Pathophysiological factors associated with AKI are also incriminated in the failure of other organs, indicating that AKI is often part of a multiple organ failure syndrome. The management of patients with AKI is principally supportive. Renal replacement therapy (RRT) was indicated for patients with severe kidney injury and multiple modalities of RRT are currently available. These include intermittent hemodialysis, continuous renal replacement therapies, and hybrid therapies, such as sustained low-efficiency dialysis. This article reviews current knowledge regarding the optimal timing, appropriate type of modality and dosing strategy for patients with AKI who require RRT.