It is widely assumed that a deficiency of immune function underlies the coexistence of viral excretion and specific-antibody production in patients with congenital rubella. Recent demonstrations of lymphocyte viræmia, and of lymphocyte competence for response to phytohæmagglutinin, have made this assumption more questionable. Whether or not the cellular immune system is unresponsive to rubella virus, cellular viræmia can be expected to continue for the lifespan of the infected cell.