The effect of fatty acid composition on odour-active compounds in brown trout (Salmo trutta) muscle was evaluated. The fillets were obtained from three groups of fish fed experimental diets containing either fish oil (170), soybean oil (SO) or linseed oil (LO). Muscle fatty acid composition was shown to be influenced by diet. Thirty-one odorous compounds were detected by gas chromatography/olfactometry (frequency-of-detection method). Most of these compounds were formed by the oxidation of unsaturated fatty acids. Independently of diet, (E)-2-pentenal, (E)-2-pentenol and (E)-2-hexenol contribute strongly to the odour of brown trout. (E,Z)-2,4-Heptadienal was detected with high frequency in fish fed diets containing high levels of n-3 PUFAs (FO and LO groups). Hexanal, (E)-2-hexenal and 2-nonanol seem to contribute most to the odour of fish fed diets containing vegetable oils. Many odorous compounds were derived from the oxidation of mono- and di-unsaturated fatty acids, which could be promoted by high levels of PUFAs.