A Salmonella enterica serovar Enteritidis epidemic in the United States began in 1978, spread to much of the country in the following decade, and began declining in 1996. We examined correlations between annual changes in S. Enteritidis incidence in humans and introductions of egg quality assurance programs (EQAPs) in some states to reduce S. Enteritidis contamination of eggs. Before EQAPs, 62% of the changes in S. Enteritidis incidence were higher than the baseline for each state. After EQAPs, 73%-84% of the changes were below the baseline. Regression analysis showed that a 1% increase in the number of eggs produced under an EQAP was associated with a 0.14% decrease in S. Enteritidis incidence (p < 0.05). These data indicate that EQAPs probably played a major role in reducing S. Enteritidis illness in these states.