Apolipoprotein (apo) E modulates the catabolism of chylomicrons and of very low density lipoprotein remnants. It has three major isoforms (apo E2, E3, E4) and some rare variants. To detect the variants of apo E, blood specimens from 1269 Japanese subjects were analyzed using isoelectric focusing with immunoblotting. The E5 and E7 variants were identified by IEF in 2 and 18 subjects, respectively. Both E5 (Glu3-->Lys) carriers were confirmed by PCR-mediated site-directed mutagenesis, and all E7 (Glu244-->Lys, Glu245-->Lys) carriers were confirmed by the amplification refractory mutation system. The relative frequencies of the epsilon 5 and epsilon 7 alleles were 0.001 and 0.007, respectively. High concentrations of total cholesterol (> 220 mg/dl) were detected in five of the subjects expressing apo E7 and one subject expressing apo E5, and eight subjects heterozygous for apo E7 showed elevated plasma triglyceride concentrations (> 150 mg/dl). In 621 healthy subjects, the mean triglyceride concentration in subjects with apo E7/3 appeared to be higher than in those with apo E3/3, but the difference was not statistically significant.