['BK virus (BKV) is known to be associated with nephropathy. Here, we investigated the relationships between BKV levels, T-cell activation, and kidney function in kidney transplant recipients.', 'In renal transplant patients and controls, urine BKV levels were detected by quantitative real-time PCR, and the percentage of activated T lymphocytes in blood was determined by flow cytometry. The correlations between viral load, activated T cell percentage, and renal function were determined.', 'Urine BKV viral loads and the activated T cell percentage were significantly elevated in transplant recipients. Correlational analysis indicated that transplant recipients that had BKV levels of more than 10(6) copies/mL and an activated T lymphocyte percentage of less than 20% were likely to have poor renal function.'] Is renal dysfunction by BK virus infection correlated with activated T cell level in renal transplantation?