Here, we evaluate an automated, direct binding surface plasmon resonance (Biacore (R) C) biosensor assay for the determination of total IgG in hyper-immunised ovine serum for use within the biopharmaceutical industry for production of polyclonal Fab fragments, including the FDA approved polyclonal biotherapeutic CroFab (TM) (Crotalidae Polyvalent Immune Fab). Serum IgG concentrations were evaluated using recombinant Streptococcus protein G immobilised to the carboxymethyl dextran matrix of a CM5 sensor chip. Ligand immobilisation, sensor surface regeneration and ovine IgG binding responses were evaluated and the suitability of the method for the screening of large numbers of ovine serum samples within a quality control analytical laboratory discussed. The report describes the evaluation and application of a simple, sensitive and rapid assay for determination of total ovine polyclonal IgG that may also be applicable for the determination of antibody concentration within serum or crude supernatants produced by recombinant or transgenic technologies used for biotherapeutic antibody production. (c) 2005 Elsevier Ltd. All rights reserved.