BACKGROUND: Patients under extra-corporeal membrane oxygenation (ECMO) are at high risk of developing acute kidney injury and renal replacement therapy (RRT) is frequently needed. The aim of this study was to explore RRT use in ECMO patients, as no recommendations exist in this setting. METHODS: An online questionnaire about RRT management in ECMO patients was sent to the members of the ARCOTHOVA (Anesthésie-Réanimation Coeur-Thorax-Vaisseaux) association and to the GFRUP (Groupe Francophone de Réanimation et Urgences Pédiatriques). RESULTS: Ninety intensivists from adult ICU and twenty from paediatric ICU responded to the questionnaire. RRT use was common as 67% respondents reported that more than 25% of their ECMO patients needed RRT. RRT indications were similar between centres, with persistent anuria (83%), metabolic acidosis (80%), fluid overload (78%) and hyperkalaemia (80%) being the more prevalent. Continuous renal replacement therapy was the preferred technique (97%). Continuous veno-venous haemofiltration was predominant (64%) over continuous veno-venous haemodiafiltration (21%). Unfractionated heparin was employed as first line choice anticoagulation in 61% and regional citrate anticoagulation in 16%. Integration of RRT device directly into the ECMO circuit was the preferred configuration (40%) while parallel systems with separate catheter were used in 30%. When the integrated approach was chosen, RRT device was most frequently connected with inlet and outlet lines after the ECMO pump (58%) and pressure alarms were encountered for 60% of participants. CONCLUSIONS: Our results highlight the high variability of practice between centres. They suggest the need to compare the integrated and parallel configurations of combining RRT and ECMO.