The correlation between the level of fructosamine and glycated proteins, including glycated lipoproteins, in serum from diabetic and nondiabetic subjects was studied. Assay of glycated proteins in serum was performed using an agarose gel film electrophoresis with nitroblue tetrazolium coloration. Glycated albumin correlated well with the fructosamine level in the diabetics (r=0.83-0.92, p<0.01) but showed no correlation with the nondiabetics (r=0.25-0, 26). Also, a high correlation between the glycated β-lipoprotein and fructosamine levels was observed in diabetic patients with hyperglycemia and in nondiabetic subjects with a high risk of atherogenesis (atherogenic index, low-density lipoprotein-cholesterol/high-density lipoprotein-cholesterol >2.8) (r=0.51-0.66, p<0.01). Nondiabetics with a high level of β-lipoprotein, which is well known to cause high atherogenesity, showed a high level of glycated β-lipoprotein similar to that in the diabetic groups with hyperglycemia; therefore, the high level of glycated β-lipoprotein seems to be attributable not only to the hyperglycemia-accelerated glycation of β-lipoprotein but also to an increase in the level of β-lipoprotein in serum.Consequently, the present results show that the fructosamine level in serum reflects not only the glycation of albumin but also that of lipoproteins which are known to increase in diabetes mellitus.