In 1987, public health authorities reported an association between human illness casued by Salmonella enteriditis (SE) and the consumption of whole grade A shell eggs. Laying hens infected with SE were subsequently found to sometimes produce very small numbers of internally contaminated eggs, but improper handling and inadequate cooking can combine to create a significant disease threat. Reducing the incidence of SE infections in chickens has accordingly become an objective of high priority for the poultry industry. Research on ths important subject at SEPRL was initiated promptly in 1987. SEPRL researchers have played a pivitol role in documenting many significant aspects of the pathogenesis, detection, and control of SE infections in chickens. Technology developed at SEPRL has provided practical tools for detecting SE contamination of eggs, identifying strains more likely to contaminate eggs, assaying for specific antibodies to identify infected hens, and testing mice in laying houses to detect the presence of virulent forms of SE. Current SEPRL research focuses include understanding the nature and significance of genetic diversity among SE isolates and identifying the sources, reservoirs, and means of transmission and control of SE in poultry flocks.