The aim of the study was to investigate apolipoprotein(apo) E polymorphism and its relationship with serum lipids and apolipoprotein, serum high density lipoprotein(HDL) subclasses in patients with type IV hyperlipidemia.apoE genotype was assayed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The subclasses of serum HDL in 103 patients with type IV hyperlipidemia and 146 normolipidemic subjects were determined by two-dimensional gel electrophoresis in conjunction with immunodetection method.The apoE3/3 genotype frequency and allele epsilon 3 frequency were both the highest in the frequency distribution profiles of the type IV hyperlipidemia group and the control group. In type IV hyperlipidemia group, the genotype of apoE2 had higher serum HDL-C,apoE, HDL(2a) apoE/apoCIII ratio but lower TG/HDL-C,apoCIII, HDL(3c) levels when compared with the genotype of apoE(3) (P<0.05). In control group, the genotype of apoE(2) had higher serum TG, apoE levels and apoE/aopCIII ratio but lower HDL (3a) level when compared with the genotype of apoE(3) (P<0.05).An association of allele epsilon 2 of apoE gene with the maturation of HDL in type IV hyperlipidemia was noted in the study.