Different ligand densities of monoclonal antibody (Mab) CB.Hep-1 were studied during covalent coupling on Sepharose CL-4B for recombinant hepatitis B surface antigen (rHBsAg) immunoaffinity purification. Ligand densities of 2.2, 3.2, 4.2 and 5.2 mg Mab/ml immunosorbents, respectively, were assayed during five cycles of immunoaffinity chromatography (IAC). Adsorption capacities averaged either 3.2 mg/ml (0.57 mg rHBsAg/ml immunosorbent/5.42 mg of total purified protein) or 5.2 mg/ml (0.56 mg rHBsAg/ml immunosorbent/5.05 mg total purified protein). Immunosorbents showed ligand leakage levels below 3 ng Mab/microg rHBsAg. Antigen purity was higher than 95% in all cases. The results suggest that a ligand density (LD) of 3.2 mg Mab/ml immunosorbent should be used for immunoaffinity chromatography because no significant differences were found in the ligand densities studied (P-value=0.012), which saves 40% of CB.Hep-1 immunosorbent manufacturing cost in comparison with 5 mg Mab/ml immunosorbent, which is currently used in large-scale production.