*Purpose: Despite rapid medical advancements in the field of transplantation over the last decades, long-term kidney allograft survival only slowly improves. Especially little is known about those kidney transplant recipients (KTRs) with very long-term survival of more than 20 years.

*Methods: We followed 271 KTRs with kidney allograft survival of more than 20 years on a quarterly/yearly basis in our kidney transplant outpatient clinic. KTRs were analyzed for patient and kidney allograft outcomes.

*Results: Our 271 KTRs with a median age of 59 years (range 38-89) at 20 years post-transplant showed a median kidney allograft function of 51 ml/min/1.73m² (range 11-103) and median proteinuria of 236 mg/day (range 0-7260). Patient survival was 84%, 63%, and 52%, and death-censored kidney allograft survival was 85%, 76%, and 61% at 25, 30, and 35 years post-transplant, respectively. We identified 104 KTRs (38.4%) with superior kidney allograft function defined as eGFR >45 ml/min/1.73m², proteinuria <300mg/day, and eGFR slope <2ml/min/1.73m². The only independent factor associated with superior kidney allograft function at 20 years post-transplant was donor age with 25 vs. 37 years (p<0.001). Patient survival was 92%, 65%, and 52% among KTRs with superior kidney allograft function compared with 85%, 62%, and 57% among KTRs with inferior kidney allograft function at 25, 30, and 35 years, respectively (p=0.420). Death-censored kidney allograft survival was 98%, 95%, and 83% among KTRs with superior kidney allograft function compared to 78%, 59%, and 39% among KTRs with inferior kidney allograft function at 25, 30, and 35 years, respectively (p<0.001). The only independent factor associated with kidney allograft loss was the development of de novo DSA (p=0. 019).

*Conclusions: While younger donor age is highly associated with superior kidney alloraft function in the very long-term, the development of de novo DSA strongly impacts kidney allograft survival. Surprisingly, ultimate patient survival did not differ between KTRs with superior and KTRs with inferior kidney allograft function at 20 years after transplantation.

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