Three dysbetalipoproteinemic subjects with the E 2/2 homozygous phenotype were analysed serum lipoproteins and serum apolipoprotein E and B levels. Two subjects were normocholesterolemic and one was hypercholesterolemic (type III hyperlipoproteinemia). A patient with type III phenotype had cholesterol-rich VLDL, although the other two normocholesterolemic subjects didn't have it. Both normo- and hypercholesterolemic subjects had elevated levels of serum apo E and a reduction in serum apo B. Therefore, serum apo E/apo B ratio of a patient with type III phenotype was extremely high as compared with other lipoprotein disorders. These ratio of normocholesterolemic dysbetalipoproteinemia was also high as compared with those except for type V hyperlipoproteinemia. It is suggested that dysbetalipoproteinemia might be easily caught in general population by screening examination of serum apo E/apo B ratio.