The detection of cytomegalovirus (CMV) infection and monitoring of its management is extremely important, particularly in immunocompromised patients.The recent increase in the use of polymerase chain reaction (PCR) diagnostics in Czech laboratories has brought the need for assessing and comparing the data using the external quality control program (EQCP) for CMV DNA detection by PCR. The aim of the National Reference Laboratory (NRL) for CMV was to introduce the EQCP on CMV DNA diagnostics in the Czech Republic.