Neonatologists' ultimate goal is to achieve a functional outcome in preterm infants that is comparable to outcomes in healthy term-born infants. Current guidelines recommend the initiation of amino acid administration as soon as possible in the first postnatal day at a dose of 2-3 g/kg/day. Within the next few days, amino acid intake should be increased to a maximum amount of 4 g/kg/day. However, actual intakes are still lower than target intakes in many neonatal intensive care units worldwide. Subsequently, many preterm infants fail to grow well, which is associated with long-term consequences with regard to growth and neurodevelopment. While most studies on early amino acid administration show beneficial effects predominantly on short-term outcomes, some studies also warn of adverse effects, especially in extremely immature and extremely low birth weight infants. Future studies should be directed towards elucidating the long-term anthropometric and neurodevelopmental outcomes of early (high dose) amino acid administration.