One hundred and twenty-eight broiler chickens divided into four experimental groups were fed diets containing soyabean or rape seed oil alone or mixed with fish oil at a ratio of 95:5. In diets and the breast and leg muscle the fatty acids (FA) profile was determined. FA profile depended mainly on the type of added vegetable oil. The PUFA/MUFA ratio in feeds, modified by the addition of fish oil, affected mainly the ratio of poly- to monounsaturated FA in the breast muscle, whereas the UFA/SFA ratio had a greater effect on the leg muscles. This confirms the varied sensitivity of muscles differing in lipid content to dietary fat quality. In the muscles of chickens given fish oil, a small amount of docosahexaenoic acid was found. However, the amount of the supplement used (0.1–0.2% fish oil) seemed insufficient to alter the FA profile in broiler muscle to an extent desired from the dietetic standpoint.