Complete DiGeorge anomaly is characterized by athymia, congenital heart disease, and hypoparathyroidism. This congenital disease is fatal by age 2 years unless immune reconstitution is successful. There are multiple underlying syndromes associated with complete DiGeorge anomaly including 22q11 hemizygosity in approximately 50%, CHARGE association in approximately 25%, and diabetic embryopathy in approximately 15%. Approximately one-third of patients present with rash and lymphadenopathy associated with oligoclonal "host" T cells. This condition resembles Omenn syndrome. Immunosuppression is necessary to control the oligoclonal T cells. The results of thymus transplantation are reported for a series of 50 patients, of whom 36 survive. The survivors develop naïve T cells and a diverse T cell repertoire.