Immunoglobulin levels in the sera of 8 newborn infants with congenital cytomegalic inclusion disease (C.I.D.) were compared with immunoglobulin levels found in normal newborn infants. IgG levels in diseased babies were normal and IgM levels were significantly higher than normal. IgA was not detectable in the sera of normal newborns but was present in every infant with C.I.D. (range 18—74 mg/100 ml). It remains to be seen if specific antibody against cytomegalovirus is present in this immunoglobulin fraction.