Report titled Multi-Centre UK NANB Surrogate Marker Study. Comprised of four volumes Volume 1 Serum Alanine Amino-Transferase (ALT) Levels in Blood Donors; Volume 2 Anti-HBc testing in UK Donor Population (two copies included); Volume 3 Clinical Evaluation of UK Blood Donors with raised Serum Alanine Aminotransferase Activity; Volume 4 Report on Evaluation of Ortho HCV ELISA Test System. Outlines background, aims, materials and methods, results and discussion of studies. Issues discussed include prevalence, self-exclusion, lack of confirmatory tests, window period infectivity, and high-risk groups.