Two infants with congenital rubella associated with diabetes mellitus were born six months apart in the same geographical area. Both mothers had contracted rubella during their sixth week of pregnancy. Both infants had subnormal birth weights and developed the classical congenital rubella defects. They represent the earliest reported onset of diabetes in association with rubella. It is notable that one of the patients did not have a family history of diabetes, thereby engendering the inference that congenital rubella can effect pancreatic development resulting in diabetes without genetic predisposition. One can postulate that rubella causes a reduction in the number of beta cells in the pancreas, thus inhibiting the production of insulin.