RECENT observations have indicated that disorders of the immune system must be added to the spectrum of congenital anomalies that are associated with prenatal infection by the rubella virus. Impaired responses of blood lymphocytes to mitogens1and antigens,2depressed delayed cutaneous hypersensitivity,2and abnormal concentrations of serum immunoglobulins3have been reported, and, although these derangements usually disappear when virus shedding ceases, some instances of long-lasting immunologic abnormalities have been described.2-6An unexplained feature of the syndrome is the persistence of virus infection in the presence of high titers of antirubella antibodies. This report describes a child with the rubella syndrome and an immunologic defect typical of dysgammaglobulinemia, type I. In addition to characterization of the immune responses of the patient, various components of the disturbed host-virus relationships of the rubella syndrome are discussed, and mechanisms for their development are proposed. Report of a Case A