K idney transplantation is the optimal therapy for end-stage kidney disease but requires lifelong immunosuppression. Despite improvements in immunosuppression regimens that have reduced rates of acute transplant rejection, long-term allograft survival remains suboptimal. More than 50% of transplanted kidneys from deceased donors fail within 10 years. In order to improve long-term outcomes, physicians need to better understand mechanisms underlying transplant rejection and tolerance in humans. They also need biomarkers that differentiate patients likely to maintain excellent and stable allograft function from recipients at risk of losing their transplants. By studying kidney transplant recipients at high risk for graft loss and rare, spontaneously tolerant kidney transplant recipients, researchers reporting in 3 papers in this issue of the JCI shed new light on these topics.