The purpose of this work was to compare hybridization and PCR methods as diagnostic tests in diagnosing and monitoring CMV infection. The investigation was performed in a group of 24 renal transplant recipients treated with ATG. The results we obtained suggest that quantitative variant of hybridization is more useful in diagnosing the infection than PCR, because it enables to monitor the infection. DNA CMV level of about 60 pg/ml or the increasing level in the subsequent samples should be a sign to start antiviral therapy.