Forty-four thousand newborn infants were screened for congenital hypothyroidism from Dec '79 to Sept. '81 in Gunma. Four patients diagnosed by this screening program. The incidence of congenital hypothyroidism in Gunma was 1 : 11, 000, which was slightly smaller than that in Japan. We diagnosed and have treated three patients.Case 1. girl. 45 day-old. She didn't presented no clinical symptoms. Bone maturation was normal. The concentration of TSH was moderately elavated, but T3 and T4 levels were normal. The thyroid scintigram presented ectopic thyroid gland.Case 2. girl. 15 day-old. The serum TSH was markedly elavated, but T3 and T4 levels were normal. She had some clinical symptoms-constipation, poor weight gain, poor activity, and muscular hypotony. Thyroid scanning demonstrated ectopic uptakes. She was treated with 1-thyroxine.Case 3. girl. 14 day-old. Serum TSH was markedly elavated, and T3 and T4 were very low. Bone maturation was delayed and some mild clinical symptoms presented-poor activity, constipation, persistent neonatal icterus, and umbilical hernia. Because the thyroid acintigram demonstrated normal uptakes, the disorder of enzymes for thyroid hormone synthesis was suspected. She treated with 1-thyroxine as case 2.At present, case 1, 2. and 3 was 18 month-old, 4 month-old, and 3 month-old, respectively. All cases have presented normal neurological development and somatic growth.