A newborn infant with large bilateral cervical masses developed respiratory difficulties three days after birth. A congenital goiter was suspected and a biopsy was performed. Later information pointed to the ingestion of large amounts of inorganic iodine, during the pregnancy, by the asthmatic mother. Further investigation proved the goiter to be due to transient depression of peroxidase activity by the exogenous iodine. Within several days after birth, the infant's thyroid regained its full activity, the goiter disappeared, and the few signs of hypothyroidism subsided.