BK virus associated nephropathy {BKVAN} is becoming increasingly recognized as a cause of renal dysfunction and loss of transplanted kidney in transplant patients with a prevalence of 1-9%The definitive diagnosis of BKVAN disease requires renal biopsyCurrent efforts to evaluate non-invasive tests for the diagnosis of BKV infection include urine cytology and PCR assay of blood, urine and tissue.He urine cytology is a good screening tool but is not diagnostic of BKVAN and the use of BKV DNA PCR has been shown to have high specificity and sensitivity.We aimed to evaluate the diagnostic value of urine cytology for detecting decoy cells versus PCR in detection of polyoma BKV in the urine of renal transplant rejection patints.The study included 20 patients urine samples form each patient were subjected to Papanicolaou staining for illustration of decoy cells in urine and PCR for detection of BKV DNA.According to decoy cell results and PCR results only 1 patient {5%} was both decoy and PCR positive and the remaining 19 patients {95%} were both decoy cells and PCR negative.So our study underlines the importance of decoy cells and PCR for the detection of BKVAN