This study details methods of production, purification and testing of large volumes of uniformly potent, non-toxic, anti-human thymocyte globulin (ATG). Plasma from 70 goats immunised with human thymic lymphocytes was fractionated by ammonium sulphate precipitation to its IgG component. Contaminating antibodies were removed by absorption methods. After fractionation and absorption, ATG retained its ability to inhibit the formation of rosettes by human lymphocytes with sheep red blood cells. Antibodies to human glomerular basement membrane were not detected in any tested preparation. Tests performed on monkeys, mice and rabbits revealed low toxicity.