BACKGROUND: Our objective was to the describe indications, management, complications and outcomes of renal replacement therapy (RRT) in COVID-19 critically ill patients. To contextualise these findings, comparisons were made against 36 non-COVID-19 consecutive patients requiring RRT on ICU. METHODS: We conducted a retrospective single centre observational cohort study of patients requiring acute RRT between 1st March and 30th June 2020. Comparison was made against those receiving RRT in the pre-COVID-19 period from January 2019 to February 2020. RESULTS: Of 154 COVID-19 patients, 47 (30.5%) received continuous venovenous haemofiltration (CVVHF), all of whom required mechanical ventilation and vasopressor support. The requirement for RRT was related to fluid balance rather than azotaemia. Compared to 36 non-COVID-19 patients, those with COVID-19 were younger (p=0.016) with a lower serum creatinine on hospital admission (p=0.049), and lesser degrees of metabolic acidosis (p<0.001) and lactataemia (p<0.001) before initiation of RRT. In addition, the duration of RRT requirement was longer (p<0.001). Despite lower CVVHF exchange rates with higher serum creatinine levels following RRT initiation in the COVID-19 patients, metabolic abnormalities were corrected. Hospital mortality was 60% among COVID-19 patients requiring RRT, compared to 67% in non-COVID patients (p=0.508), and renal recovery among survivors without pre-existing CKD was similar (p=0.231). CONCLUSIONS: The requirement for RRT in COVID-19 patients was primarily related to fluid balance and using lower CVVHF exchange rates was effective to correct metabolic abnormalities. Renal recovery occurred in all but one patient by 60 days in the 40% of patients who survived.