Maternal hyperthyroidism implies the risk of thyroid abnormalities in the newborn. We describe retrospectively the clinical presentation, treatment and follow up of 28 children born of hyperthyroid mothers. Patients were subdivided as follows: Group A (neonatal hyperthyroidism) (n=9): born from eight hyperthyroid mothers and one thyroidectomized mother. Children born from untreated mothers consulted between 1 and 7 days of life, while those born from treated mothers consulted between 8 and 17 days. Eight needed treatment. All remitted completely. Group B (primary hypothyroidism) (n=14): born from treated mothers, detected by neonatal screening. Eleven had transient hypothyroidism and three needed treatment. Group C (hypothalamic-pituitary hypothyroidism) (n=5): born from uncontrolled hyperthyroid mothers and found during follow up (age 9-28 days). The infants were treated with thyroid hormone, and recovered before 8 months of life. Every child born from a mother with autoimmune thyroid disease needs paediatric endocrinological assessment for detection of possible thyroid disorders.