It is widely accepted that the cause of congenital deafness is genetic in one third of cases roughly, is due to acquired affections during pregnancy or delivery in another third and remains unknown in the last third. It is possible that the cytomegalovirus (CMV) plays an important role in the latter group. The CMV is thought to be involved in 10 to 30% of cases of auditory sequelae from fetal infection, either severe neonatal CMV-induced disease, which is rare, or the frequent subclinical infections affecting an average of 1% of newborn infants. The only certain way to determine the importance of the role of CMV in deafness of unknown etiology is large-scale neonatal biologic screening followed by long-term audiologic surveillance: currently available documented data suggest that this role is very important.