Abstract: A sensitive and specific solid phase radioimmunoassay for hepatitis B core antibody(anti-HBc-RIA) is established. Hepatitis B core antigen(HBcAg) is coated on the solid phase beads, ~(125)I-anti-HBc is used as the radioactive tracer. The sensitivity of the assay is 0.8 NCU/mL. The intra-assay CVs and the intre-assay CVs of 3 samples are 9.9% and 13.8% respectively. The analytical recoveries are ranged from 92.6% to 109.2%. The level of 120 normal subjects is 1.2 NCU/mL with a rang of 0~2.0 NCU/mL. The method for measuring anti-HBc in human serum is rapid, sensitive, convenient and inexpensive. It is suitable for clinical and research application.