The fatty acid composition and omega 3/omega 6 ratios in the muscle of wild and reared Oncorhynchus mykiss (rainbow trout) in the Tohma River (Sivas, Turkey) were determined by gas chromatography. There were quantitative differences between some fatty acids in the muscles of wild and reared rainbow trout. The most abundant fatty acids in both wild and reared fish were palmitic acid (16:0), stearic acid (18:0), oleic acid (18:1 omega 9), and docosahexaenoic acid (22:6 omega 3). The levels of omega 3 series and omega 6 series fatty acids in wild fish muscle were higher than in the reared fish. The omega 3/omega 6 ratios in muscle were found to be 1.92 (reared fish) and 2.28 (wild fish). The higher omega 3/omega 6 ratio in the wild fish might be a result of the season and the richer feeding conditions in the river under natural conditions. However, daily and continuously reared fish might be turned into more beneficial food for human consumption.