Apo (E-AII) complex (a disulfide complex of monomers of apoE and ApoAn) and apoE in human apoVLDL showed microheterogeneity in molecular weight and isoelectric point on two dimensional gel electrophoresis. It was found that the apo (E-MI) complexes reveal isoforms related to apoE phenotypes and a minor portion of the complexes and apoE constitute sialylated isoforms. In the two dimensional gel electrophoretic patterns on phenotypes of E3/E3 and E2/E2, apo (E3-A11) complex or apo (E2-A II) complex with its sialylated isoforms were observed, whereas in phenotypes of E3/E2, both apo (E-A II) complex isoforms were found. In phenotypes of E4/E3 or E4/E2, only a band of apo (E3-AII) complex or apo (E2-A II) complex was found, with relatively poor intensity, and no apo (E-AII) complex was detected in phenotype of E4/E4, probably because of the absence of cysteine residue in the apoE4 molecule.