To examine the characteristics of hepatitis B virus (HBV) in sera from hepatitis B patients in various stages of disease, the protein volume percent of each constituent peptide of HBV was investigated, and both the HBV-pAR activity and HBsAg activity of each peptide were examined. The relationship between HBV, immunoglobulins and complements was also investigated. The constituent peptides were divided into a few bands of more than 94Kdal., 3 bands of 94~67Kdal. and 12 bands of 67, 52, 49, 43, 39, 35, 31, 27, 22, 19, 15 and 8Kdal.. The samples of HBeAg positive sera showed increased 22, 27, 31, 35 and 67Kdal. bands, and the samples of anti-HBe positive sera showed decreased 22 and 27Kdal. bands and increased 15 and 43Kdal. bands. The samples of sera from asymptomatic carriers showed an increased 43Kdal. band, and that from patients with chronic active hepatitis showed an increased 15Kdal. band. HBV-pAR consisted of 67, 52, 43, 35, 31 and 8Kdal. peptides, and the determinants of HBsAg consisted of 67, 52, 49, 43, 39, 35, 31, 27 and 22Kdal. peptides. HBV-peptides of 67, 52 and 22Kdal. bound with immunoglobulins and complements in Western-blotting.