AbstractNine hundred and ninety‐eight obese children aged 6 to 15 years participated in the present study. Fasting serum lipid and lipoprotein cholesterol values were measured and the relationship between obesity and abnormalities of serum lipids and lipoproteins was assessed. The results were as follows: 1. Obese children were more likely than non‐obese children to have elevated serum total cholesterol (TC), triglyceride (TG) and LDL‐C(low density lipoprotein cholesterol) levels and reduced HDL‐C (high density lipoprotein cholestrol) levels. 2. The more the relative body weight index increased, the worse the abnormalities of serum lipids and lipoproteins became. This tendency was marked in junior high‐school boys. 3. Hypercholesterolemia in obese children was mostly accounted for by LDL‐C only and elevated HDL‐C could no