OBJECTIVE To evaluate the effects of levothyroxine (L-T4) supplementation on growth and neurodevelopmental outcomes at 3 years of age in very low birth weight (VLBW) infants with transient hypothyroxinemia of prematurity (THOP). STUDY DESIGN VLBW infants with plasma thyroid-stimulating hormone concentrations <10 mIU l-1 and free thyroxine concentrations <0.8 ng dl-1 were defined as having THOP and randomly assigned to the Treated (20 infants) or Untreated (31 infants) group. The Treated group received L-T4 at a dose of 5 μg kg-1 day-1. Growth and neurodevelopmental outcomes at 3 years of age were compared between the two groups. RESULTS There were no significant differences in body length, body weight or head circumference mean s.d. scores or in neurodevelopmental outcomes between the two groups. CONCLUSION L-T4 supplementation in VLBW infants with THOP demonstrated no beneficial effect at 3 years of age.