A feeding experiment was conducted to determine the requirement of fingerling white fish Coregonus lavaretus maraena for dietary n-3 fatty acids. Growth, and feed efficiency together with survival rate were lowest in fish receiving a diet containing 5% 18: 1n-9 as a sole lipid source; all parameters were effectively improved by supplementation of linolenic acid (18: 3n-3) or n-3 highly unsaturated fatty acids (n-3 HUFA), and highest in fish fed a diet containing n-3 HUFA greater than 0.5%. The liver lipid content was highest in fish fed the 18: 1n-9 diet, and was effectively reduced by supplementation of n-3 HUFA by more than 1.0%, but not by 18: 3n-3 even at a level of 2%. Dietary 18: 3n-3 was converted to 22: 6n-3, but the percentage of 22: 6n-3 in the liver polar lipid of fish fed 1 and 2%. 18: 3n-3 was much lower than that of fish fed 0.25%. n-3 HUFA. The data obtained in the present study indicate that n-3 fatty acids are essential for white fish and that the EFA value of n-3 HUFA was much higher than that of 18: 3n-3. The requirement of fingerling white fish for dietary n-3 HUFA was found to be around 1%.