Given the limited information regarding BK virus-associated nephropathy (BKVN) in pediatric kidney transplant recipients, we assessed the incidence, risk factors, clinical and virologic features of BKVN in pediatric renal transplant recipients at a single transplant center by means of a retrospective cohort study. Histologically confirmed BKVN developed in 6 of 173 (3.5%) kidney transplant recipients at a median of 15 months post-transplant (range: 4-47 months). At a median follow-up of 28 months (range: 5-32), all patients had functioning grafts with mean creatinine and GFR of 1.9 mg/dL and 58 mL/min/1.73 m2, respectively. At the time of diagnosis, all cases had viruria (median 6.1 x 10(6) copies/mL, range: 10(5) to 3.9 x 10(8) copies/mL) and viremia (median 21,000 copies/mL, range: 10,000-40,000 copies/mL). Recipient seronegativity for BKV was significantly associated with the development of BKVN (p = 0.01). BKVN is an important cause of late allograft dysfunction and is strongly associated with recipient seronegativity in pediatric kidney transplant recipients. Further studies to confirm this finding and to define the clinical utility of routine pre-transplant BKV serologic testing are warranted.