No immunologic explanation has been found for the chronicity commonly observed in congenital viral infections. In the presence of a humoral immune response, there is continued viral excretion--in rubella for many months, and in the herpes viruses perhaps for life. Infection with rubella early in utero has a profound effect on the developing immune system. Defects observed are: complete immune paralysis, PHA unresponsiveness, immunoglobulin abnormalities, and loss of antibody to rubella. These defects are transient; absence of IgA may be permanent. No such defects have been observed in other congenital viral infections, but precocious development of immune globulin levels and germinal follicles occurs.