This paper summarises the current evidence on neuro-developmental deficits in the early (< 1 month of age) treated congenital hypothyroid and the influencing factors. A literature search revealed only few citations that compared outcome with matched controls. In all but one, the median age of treatment onset was >2 weeks. Mean Global IQ scores are about 10 points lower and remain identifiable in adulthood. Verbal and performance scores are usually similar. Deficits persisting into adolescence and adulthood involve the visuomotor, memory, attention and posture domains. Lower academic performance is common in the early years. Prenatal factors associated with a worse prognosis are aetiology (dysgenesis), low birth weight, associated complications and severity of hypothyroidism. Postnatal factors are age at onset of treatment (>1 month), lower thyroxine dose at onset (<8 mcg/kg/day), late normalisation of thyroid function (>2 weeks after treatment), and a lower socio economic family status. The author proposes the evaluation of a multi centre cohort with a median age of treatment onset <1 week, TSH normalisation by <3 weeks with treatment thyroxine levels maintained in the 3rd quartile for age. The outcome of this cohort should indicate if current targets in management need to be revised.