Background/Aim. More than 90% of worldwide population is infected with human cytomegalovirus (CMV), one of the most common agents which complicate immunocompromised patients. Viral infections, in particular CMV ones are still a major cause of moratality and morbidity after stem cell transplantation (SCT). Monitoring is performed by detecting CMVAg or virus DNA in peripheral blood. Risk factors are donor/ recipient CMV status, type of transplant and acute graft versus host disease. The aim of the study was to determine the extent of validity of CMV infection monitoring after transplantation as a reliable parameter of further CMV replication course in patients with hematopoietic stem cell transplantation. Methods. A total of 49 patients with stem cell transplantation were studied prospectively during a 2-year period after transplantation for the presence of CMV DNA. Polymerase chain reaction (PCR) CMV DNA was performed on 222 full blood samples using Cobas Amplicor assay. Results. Activation of CMV was detected in 10/49 (20.48%) of the patients. The median posttransplantation time for the first positive PCR result was 6 weeks for the stem cell transplant patients. Viremia became negative in all the cases after the antiviral therapy with ganciclovir. Conclusion. Our data show that the level of CMV-DNA load at the time of initial CMV detection after transplantation could be a possible predictor for further course of CMV replication in patients receiving hematopoietic stem cell.