In the normal population, the usual effect of the epsilon 2 allele is to decrease plasma cholesterol and to increase plasma triglyceride. We report here the association of nephrotic syndrome and the apo epsilon 2 epsilon 2 genotype in which we observed a hyperlipidemia characterized by very low levels of lipoprotein lipase activity, chylomicronemia, high levels of plasma apo B, C III, E and lipoprotein(a), very low levels of high density lipoprotein cholesterol and concentrations of cholesterol and triglyceride that are higher than expected in all the other lipoprotein fractions. When proteinuria was partially resolved and plasma albumin levels returned to normal, a residual type III hyperlipidemia was still present. These findings suggest that the combination of apo epsilon 2 homozygosity and massive proteinuria may cause considerable changes in the clearance of triglyceride rich particles probably mediated by the almost complete absence of lipolytic enzymes and a low interaction of lipoproteins with specific receptors. The apo E genotype should be investigated in nephrotic patients with chylomicronemia.