Background. Improvement in long-term renal allograft survival is impeded by incomplete or erroneous coding of causes of allograft loss. This study reports 13-year trends in causes of graft failure across the UK. Methods. National Health Service Blood and Transplant (NHSBT) and UK Renal Registry data were linked to describe UK kidney patients transplanted 2000-2013. NHSBT graft failure categories were used, with 'other' recoded when free text was available. Adjusted analyses examined the

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... e of age, ethnicity and donor type on causes of graft failure. Results. In 22,730 recipients, 5,389 (23.7%) grafts failed within a median follow-up of five years. The two most frequent causes were death with a functioning graft (40.8%) and alloimmune pathology (25.0%). Graft survival was higher in recipients who were younger (mean 47.3 vs. 50.7 years), received a pre-emptive transplant (20.2% vs. 10.4%), spent less time on dialysis (median 1.6 vs. 2.4 years) and received a living donor transplant (36.3% vs. 22.2%), with no differences by sex, ethnicity or human leukocyte antigen mismatch. Allograft failure within two years of transplantation fell from 12. 5% (2000-2004) to 9.8% (2009)(2010)(2011)(2012)(2013). Surgical and alloimmune related failures decreased over time while death with a functioning graft became more common. Age, ethnicity and donor type were factors in recurrent primary disease and alloimmune pathology. Conclusions. Since 2000 there have been reductions in surgical and alloimmune graft failures in the UK. However, graft failure codes need to be revised if they are to remain useful and effective in epidemiological and quality improvement trials.