Objectives: The purpose of this bachelor's thesis is to clarify the method of serological diagnosis of cytomegalovirus at the Teaching Institute for Public health of Split-Dalmatia County. Materials and methods: The procedure of serological diagnosis of CMV includes the detection of IgM and IgG antibodies. The presence of IgM antibodies indicates acute infection while IgG indicates past infection. For the diagnostic purpose, at the Teaching Institute of Public Health of Split-Dalmatia County, kits Abbott Alinity i are used to detect CMV antibody. The analyzer is also called Abbott Alinity i. The method used to determine antibodies is CMIA. CMIA is the abbreviation for the chemiluminescent immunochemical method. The sample is a serum that is extracted by centrifugation of blood. The serum is placed in a rack and then in an analyzer that analyzes the presence of antibodies. Results: Serological examination of the patient's sample determined the presence of IgG antibodies to CMV, and the absence of IgM, which indicates a past cytomegalovirus infection