Growth failure is a classical sign of essential fatty acid deficiency. We investigated whether birth weight correlates with the postnatal essential fatty acid status in a group of 29 premature infants. A significant and positive correlation between body weight and plasma triglyceride content of arachidonic acid (20:4n-6) (r = 0.47, p = 0.01) and total omega-6 long-chain polyunsaturated fatty acids (r = 0.49, p less than 0.01) was found. In contrast, there was no positive relation to linoleic acid (18:2n-6) or any omega-3 fatty acid but a significant inverse correlation to alpha-linolenic acid (18:3n-3). We propose that during early life arachidonic acid may have a growth-promoting effect which could be related to its role as an eicosanoid precursor or to its structural function in membrane lipids.