Background and objective The risk of graft loss after pediatric kidney transplantation increases during late adolescence and early adulthood, but the extent towhich this phenomenon affects all recipients is unknown. This study explored interactions between recipient factors and this high-risk age window, searching for a recipient phenotype that may be less susceptible during this detrimental age interval. Design, setting, participants, & measurements With use of Scientific Registry of Transplant Recipients data from 1987 to 2010, risk of graft loss across recipient age was quantified using a multivariable piecewise-constant hazard rate model with time-varying coefficients for recipient risk factors. Results Among 16,266 recipients, graft loss during ages ≥17 and < 24 years was greater than that for both 3-17 years (adjusted hazard ratio [aHR], 1.61; P<0.001) and ≥24 years (aHR, 1.28; P<0.001). This finding was consistent across age at transplantation, sex, race, cause of renal disease, insurance type, pretransplant dialysis history, previous transplant, peak panel-reactive antibody (PRA), and type of induction immunosuppression. The high-risk window was seen in both living-donor and deceased-donor transplant recipients, at all levels of HLA mismatch, regardless of centers' pediatric transplant volume, and consistently over time. The relationship between graft loss risk and donor type, PRA, transplant history, insurance type, and cause of renal disease was diminished upon entry into the high-risk window. Conclusions No recipient subgroups are exempt from the dramatic increase in graft loss during late adolescence and early adulthood, a high-riskwindowthat modifies the relationship between typical recipient risk factors and graft loss. © 2013 by the American Society of Nephrology.