Bacteria belonging to the genus Salmonella are a major cause of disease in both man and animals, with the pathogenesis of disease depending on the serovar of Salmonella and the host species involved. Infections with Salmonella bacteria generally result in the production of serum antibodies to somatic (lipopolysaccharide), and in certain cases also to flagellar ( H ) antigens. Serological tests, based on the detection of antibodies toSalmonella antigens can provide a valuable adjunct to established bacteriological techniques. In this article, the antibody response of humans and chickens to infection with key members of the genus Salmonella, is described.