Screening for hepatitis B surface antigen (HBsAg) demands highly sensitive and specific immunoassays with the ability to detect clinically relevant surface gene mutants-the presence of which is an increasing concern and can compromise test results. The objective of the study was to compare the clinical and technical performance of the fully automated Elecsys HBsAg II assay with other widely used HBsAg immunoassays in China. This was a multicentre study in which eight Chinese laboratories compared the Elecsys HBsAg II assay with the Architect HBsAg assay, AxSYM HBsAg assay, or generic microtitre plate (MTP) enzyme-linked immunosorbent assays (manufactured in China) against preselected samples, including recombinant surface gene mutants, and routine clinical samples. Elecsys HBsAg II was the most sensitive assay for detecting positive results in seroconversion samples: up to 14, 11, and 22 days earlier than the Architect, AxSYM, and MTP HBsAg assays, respectively. It also detected all 211 preselected HBsAg-positive specimens and all 13 recombinant HBsAg mutants; the AxSYM and MTP HBsAg assays failed to detect 3 and 10 mutant samples, respectively. Sensitivity was 100% for Elecsys HBsAg II with routine samples, compared with 99.1, 98.9, and 95.2% for the Architect, AxSYM, and MTP HBsAg assays, respectively. In conclusion, it was demonstrated that the Elecsys HBsAg II assay is suitable for routine HBsAg screening in China.