Medium-chain fatty acids are an important energy source for preterm neonates. Based on assumptions from earlier investigations, 40% to 60% of fatty acids in formula designed for preterm neonates are C6:0 to C12:0. This review will reevaluate these assumptions about C6:0 to C12:0 fatty acids. More recent investigations have indicated that when C6:0 to C12:0 fatty acids are administered in high concentrations, they are metabolized in several tissues by carnitine-dependent mechanisms. Incomplete oxidation of C6:0 to C12:0 fatty acids may result in elevated dicarboxylic acid levels. Feeding formulas high in C6:0 to C12:0 fatty acids has not improved nitrogen retention or growth of preterm neonates. Current data indicate that the fatty acid profiles of formula for preterm neonates are not optimal. Optimization of the fatty acid profile in the diet awaits an improved understanding of the metabolism of fatty acids of all chain lengths in the preterm neonate.