Background: MARS is an artificial extracorporeal liver support system allowing removal of albumin bound and water soluble toxins. MARS is expensive and efficacy of the treatment is not clear. The objective of this study was to report 30 days survival of patients treated with MARS. The experience of MARS treatment is currently registered into a prospective MARS registry. Methods: Sixty-two patients with different underlying cause of liver failure were treated with MARS in our hospital from 2005-2012 (49 adults and 13 children < 18 years). In addition to baseline biochemical parameters and demographics, we registered listing for liver transplantation, liver transplants performed as well as presentation, acute versus chronic. Survival data were compared with results from patients transplanted on the basis of acute liver failure (ALF) without MARS treatment in our unit during the period 2001-2010. Results: Median MELD-score was 36 (range 25-54) in the adult group and encephalopathy grade 4 (median) in the overall material. Time from onset of MARS treatment to transplantation was median 2 days (range 1-12) in the transplanted group (n=34). P-ammonia and bilirubin as well as creatinine and urea were significantly reduced after starting up MARS. 30 days overall survival in the adult group was 68 %, and in the pediatric group it was 77 %. Survival for transplanted (n=39) and for not transplanted (n=23) patients was 85 % and 39 %, respectively. Fourteen of all patients (22 %) were repeat transplantations. There was no increased mortality in these patients. No deaths were related to the MARS-treatment. 30 days survival for transplanted ALF was 96% (n=24) for patients not reciving MARS. However, in this group encephalopathy grade was 2 (median) and median MELD-score was 31 (range 14-40). Conclusion: MARS treatment is safe and effective in reducing known biochemical risk factors for death in patients with ALF. Thirteen children were treated with MARS and 30 days survival in these were not statistically inferior compared to adult patients.