In an experiment involving 4-week-old chickens the effects of feeding different levels of rapeseed oils of high and low erucic acid content on the weight, lipid content and fatty acid composition of various tissues was studied. The results obtained indicated that: (1) On the average, the kind of oil or fat fed did not appear to influence heart-to-body-weight ratio. Only regular rapeseed oil increased liver-to-body-weight ratio by more than 10 %. The data also show that the feeding of rations containing regular rapeseed oil or Canbra oil (a low erucic type) produced the smallest spleens while feeding rations containing soybean oil or lard resulted in the highest spleen-to-body-weight ratios. (2). The total lipid content of the heart of chickens fed regular rapeseed oil and Canbra oil-containing diets was significantly (p ≤ 0.05) lower than those receiving Span oil, soybean oil or lard-containing diets. The total lipid content of liver or spleen was not influenced by the kind of oil or fat included in the ration. (3). The fatty acid composition of the feed fats altered the fatty acid pattern of the total lipids of heart, liver, spleen and breast muscle. Feeding the rapeseed oil-containing diets led to a decrease in the concentration of saturated fatty acids in the organs with increasing additions of oil to the diets, whereas the concentration of mono-unsaturated fatty acids increased. This increase was mainly due to increases in the concentration of eicosenoic (C 20:1) and erucic (C 22:1) acids in tissue lipids. Addition of the low erucic acid rapeseed oils (Canbra and Span) to the rations led to similar but smaller changes in the composition of the tissue lipids of the chickens. Feeding increasing levels of soybean oil in the diet led to an increase in the concentration of polyunsaturated fatty acids in the total lipids of liver, spleen and breast muscle, whereas with feeding of increasing levels of lard in the diet the concentration of saturated fatty acids in these tissue lipids tended to increas