Changes in the fatty acid (FA) composition of unfed and fed rainbow trout (Oncorhynchus mykiss) larvae were determined by gas chromatography. Total lipids were extracted from samples by homogenization in chloroform/methanol (2:1, v/v). Fatty acid methyl esters were prepared from total lipid. The sample was saponified with methanolic potassium hydroxide (KOH). The fatty acids esterified with boron trifluoride-methanol (BF3-methanol) and fatty acid methyl esters were analyzed with a Shimadzu GCMSQP5000 gas chromatograph.In starved larvae, there was an apparent preference in utilization of oleic acid (C18:1 omega-9) in monounsaturated fatty acids than in the fed larvae. In both starved and fed larvae, palmitoleic (C16:1 omega-7) acid was preferentially kept during the same period. Larvae kept 29 days under starvation conditions exhausted linolenic acid (C18:3 omega-6), eicosanoic acid (C20:0), docosanoic acid (C22:0) and docosatrienoic acid (C22:3 omega-3). They utilized less eicosapentaenoic (C20:5 omega-3; EPA) acid and conserved strongly docosahexaenoic (C22:6 omega-3; DHA) acid.