Two cases of rubella embryopathy are presented. In both, hypoplasia of the thymus and of the thymus-dependent lymphoid tissue was conspicuous. Vascular lesions identical with those described in the congenital rubella syndrome were present in the thymic vessels. The coexistence of these vascular and parenchymatous lesions in the thymus suggests that the rubella virus may be the aetiological agent responsible for this type of immune deficiency disease.