The potential for increased brain Mn accumulation in infants and the potential health risks associated with elevated brain Mn burden represent crucial, unexplored issues of exposure and susceptibility. The impact of dietary Mn, and especially parenterally delivered dietary Mn, gestational age, Fe status, and hepatic dysfunction on the ability of the neonatal brain to regulate Mn deposition has not been scientifically addressed. The proposed clinical investigation has enormous health significance and may shed light on the development and progression of neurological dysfunction in infants and children on prolonged parenteral nutrition.