Acute kidney injury (AKI) is among the most common and serious complications experienced by hospitalized patients. However, the incidence of AKI has been increasing year by year. Despite significant advances in the treatment and understanding of AKI, the mortality rate of AKI has barely improved during the past few decades. So far, no specific medical treatment for AKI has been established. Therefore, renal replacement therapy (RRT) might play a key role in the treatment of critically ill patients with AKI. Several clinical issues associated with RRT for AKI are yet to be solved. There is some consensus regarding the most appropriate RRT modality (intermittent or continuous RRT) and the optimal RRT dose for AKI. On the other hand, no definitive conclusions have been reached concerning the optimal timing of the initiation and discontinuation of RRT, the use of anticoagulants during RRT, and the most suitable dialysis membranes for AKI. Thus, many problems remain. So, further aggressive investigations are needed to improve the mortality rate of patients with AKI. This review will assess the current status of and problems associated with RRT for AKI.