Acute kidney injury (AKI) with the subsequent need for renal replacement therapy (RRT) represents a persistent challenge, arising in 4-5% in critically-ill patients, and remains associated with a high mortality (60%) and morbidity. As AKI is an independent risk factor for poor prognosis, appropriate management of patients with AKI becomes of utmost importance. Complications of AKI can be treated with different forms of RRT, such as continuous veno-venous hemofiltration or intermittent hemodialysis. However, the timing of the initiation, the modality, and the dose of RRT are still controversial and the subject of ongoing clinical trials. This review presents and discusses currently available data regarding the use of RRT in critically-ill patients with AKI.