In order to assess the relationship between obesity and serum lipids, a homogenous group of adult men and premenopausal women is assessed for body mass index, body fat distribution reflected by the waist/hip ratio (WHR), serum lipid parameters and apolipoproteins. Body fat distribution is distinguished in an abdominal and gluteal-femoral type using a cut-off point of 1.00 for the ratio of waist-to-hips girth for men. In women the cut-off value is considered as 0.80 but was also evaluated when considered as 0.85. In the next step tertiles for WHR are created to show a graded relationship between WHR and lipoprotein fraction. The results indicate that WHR is an important determinant for most atherosclerosis-related lipids and apoproteins: in both men (P less than 0.05) and women (P less than 0.005) WHR is significantly correlated with apolipoprotein B. Using multiple regression analysis, in women WHR seems to be the most important dependent variable, where body mass index is not significantly contributing to the explained variance. In men, however, besides WHR age is the most significant variable, although age distribution is similar in men and women. Using tertiles of WHR, we show a clear graded relationship with most lipids and lipoproteins; this gives additionally an argument to confirm that in women WHR = 0.80 is the most accurate cut-off value for abdominal obesity. This study demonstrates that both obese men and women with an abdominal fat mass distribution show a lipid and apoprotein profile that is less favorable than that seen in gluteal-femoral obese subjects insofar as the risk of coronary artery disease is concerned