Polyomavirus-associated nephropathy (PyVAN) occurs in recipients of kidney transplantation. The development of PyVAN can cause a decrease or complete loss of the function of the kidney. Two of the human polyomaviruses BKPyV, JCPyV are known to be involved in the pathogenesis of PyVAN, and a further virus HPyV9 has been found in renal transplant recipients. A multiplex quantitative polymerase chain reaction (qPCR) for BKPyV, JCPyV, and HPyV9 DNA, together with an internal control molecule, was used to investigate polyomavirus infection in the late transplant period. Results for BKPyV, JCPyV were reported in IU/mL. The dynamic range, linearity and reproducibility of the assay was good (intra- and inter-assay variation for each viral target of