Charolaise bulls and heifers showed higher SFA and lower MUFA content of longissimus thoracis muscle (MLT) than did the Aberdeen-Angus, Simmental and Hereford cattle, with no reference to feeding. It can be assumed that this difference is due to the reduced activity of delta-9-desaturase in Charolaises. Fatty acid composition of MLT was significantly modified by feeding diets rich in n-3 and n-6 PUFAs. Both linseed and sunflower supplementation increased the proportion of CLA. In addition, inclusion oflinseed enhanced the proportion of long chain PUFA n-3 (EPA, DPA, DHA) and reduced PUFA n-6 to PUFA n-3 ratio, important for human health.