Introduction: Detection of human cytomegalovirus (CMV, HHV-5) DNA in clinical specimens is considered a cornerstone in the diagnosis of HHV-5 disease. The present study compared two quantitative methods used for diagnosing cytomegalovirus infection in a 21-year-old woman with chronic myeloid leukemia after an unrelated umbilical cord blood transplantation. Materials and Methods: Blood samples were tested for the presence of HHV-5 DNA using the LightCycler PCR, the quantitative Eclipse? CMV DNA Detection Kit, and a qualitative in-house PCR assay using primers that amplify part of the HHV-5 MIE gene. Results: Results from samples containing a low cytomegalovirus load were more accurate with the LightCycler test than those obtained with the Eclipse? test, which underestimated the viral load of samples containing low DNA copy numbers. Conclusions: These findings underline the value of novel PCR methods used in current therapeutic procedures and in monitoring antiviral therapy with nucleoside analogs. The high level of sensitivity, specificity, accuracy, and rapidity provided by the LightCycler instrument are favorable for the use of this system in the detection of HHV-5 DNA in clinical specimens.