Cytomegalovirus (CMV) causes serious illness in immunocompromised patients and congenitally infected neonates. Knowledge of the epidemiologic characteristics of CMV remains limited, but specific and practical measures can help prevent the transmission of infection to persons in high-risk groups. Good personal hygiene, especially hand washing, is the most effective means of preventing the acquisition of CMV by pregnant women and by individuals who care for children and immunocompromised patients. Screening programs for the identification of seronegative pregnant women and female hospital employees or of asymptomatic children who are excreting CMV are not practical or beneficial; educational programs are recommended instead. Since CMV infection is endemic in the community, exclusion of known CMV excretors from schools is not indicated. Exposure of premature infants or of organ transplant recipients and other severely immunocompromised patients to exogenous sources of CMV, such as blood transfusions, should be minimized. These recommendations may need to be revised in the future as more specific knowledge of the epidemiology of CMV is gained.