Among 166 congenitally hypothyroid children, 30% had a birth weight over the 90 degrees percentile of normal newborns, and 17% of those born after a full-term gestation weight 4000 g or more. The birth length was known in 84 cases and was not different from normal standards. An excess of birth weight relatively to birth length must suggest, among other factors, the possibility of congenital hypothyroidism.