CMV is a significant cause of morbidity and mortality specially in organ transplant recipients and immunocompromised individuals. Positive CMV IgG results indicate past or recent CMV infection. These individuals may transmit CMV to susceptible individuals through blood and tissue products. Individuals with negative CMV IgG results are presumed to not have had prior exposure or infection with CMV, and are therefore considered susceptible to primary infection. It is also responsible for congenital disease of the newborn. Positive IgG levels indicate past or current infection. Single IgG titre should not be used for diagnosis of recent infection. Diagnosis of primary, acute phase infection with cytomegalovirus (CMV), especially in patients with infectious mononucleosis and pregnant women who, based on clinical signs or exposure, may have primary CMV infection. CMV is also responsible for congenital disease among newborns and is 1 of the TORCH infections (toxoplasmosis, other infections including syphilis, rubella, CMV, and herpes simplex virus).