CMV is a significant cause of morbidity and mortality specially in organ transplant recipients and immunocompromised individuals. 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. Paired acute and convalescent sera should be tested for seroconversion which is indicative of primary infection or reactivation of latent infection.