Background: Extended daily dialysis (EDD) has been suggested as an effective renal replacement therapy for acute kidney injury. However, results from studies comparing EDD to continuous renal replacement therapy (CRRT) are inconclusive. Study Design: A systematic review and meta-analysis was performed by searching in MEDLINE, EMBASE, the Cochrane Library, Google Scholar, and a Chinese database (SinsoMed). Setting & Population: Patients with acute kidney injury. Selection Criteria for Studies: Randomized controlled trials (RCTs) and observational studies were included. EDD was defined as extended hemodialysis or hemodiafiltration for more than 6 but less than 24 hours per session using a conventional hemodialysis machine. Intervention: Renal replacement therapy comparing EDD with CRRT. Outcomes: Mortality, kidney recovery, and fluid removal. Results: We included 17 studies from 2000 to 2014: 7 RCTs and 10 observational studies involving 533 and 675 patients, respectively. Meta-analysis of RCTs showed no difference in mortality rates between EDD and CRRT (relative risk, 0.90; 95% CI, 0.74-1.11; P = 0.3). However, EDD was associated with lower mortality risk compared with CRRT in observational studies (relative risk, 0.86; 95% CI, 0.74-1.00; P = 0.05). There was no evidence of heterogeneity in RCTs (I-2 = 0%) or observational studies (I-2 = 15%). In both RCTs and observational studies, there were no significant differences in recovery of kidney function, fluid removal, or days in the intensive care unit, and EDD showed similar biochemical efficacy to CRRT during treatment (serum urea, serum creatinine, and serum phosphate). Limitations: The survival benefit of EDD is dependent on only observational studies and might have been affected by allocation or selection bias. Conclusions: EDD is associated with similar outcomes to CRRT in RCTs. The finding that EDD is associated with a lower mortality rate relies on data from observational studies, which are potentially subject to allocation or selection bias, making further high-quality RCTs desirable. (C) 2015 by the National Kidney Foundation, Inc.