Technetium 99m pertechnetate thyroid scans were performed on 57 infants referred for evaluation of suspected congenital hypothyroidism. Thyroid anatomy may be characterized by four general types, based on the scintigraphic findings: (1) normal size and location; (2) ectopic location; (3) no detectable thyroid activity; (4) normal location with increased size or uptake. There are diverse etiologies of congenital hypothyroidism. Correlation of thyroid scintigraphy with blood T4 and TSH levels allows specific etiological diagnosis in the majority of cases of congenital hypothyroidism.