AbstractTwo fractions, I and II, corresponding to heavy and light molecular forms of HBeAg and respectively associated with the (HBe/1 + HBe/2) and (HBe/3) specificities, were separated by ammonium sulfate precipitation in HBeAg‐positive chimpanzee plasma. I 125‐labeling of fractions I and II and immune precipitation by anti‐HBe and anti‐Human IgG were followed by autoradiographic analysis after SDS polyacrylamide gel electrophoresis:This revealed that two small peptides (a major 17,000 MW and minor 21,000 MW) seem common to the various molecular forms and specificities of HBeAg. Both peptides were found tightly linked to IgG in fraction I, associated with HBe/1 and HBe/2 and precipitated by 1.33 M (NH4)2SO4. In the HBe/3‐positive fraction II these peptides seemed attached to IgG light ch