Estimates of the cost of foodborne illness play an important role in guiding Federal efforts to prevent foodborne illness in the United States. In 2000, the U.S. Department of Agriculture's Economic Research Service (ERS) estimated that the cost of illness from five major foodborne pathogens was $6.9 billion per year. In 2010 and 2012, new comprehensive cost-of-illness estimates were published for the first time in a decade. Scharff (2010; 2012) estimated the cost of foodborne illness in the United States to be as high as $152 billion, while Hoffmann et al. (2012) estimated that illness from 14 major pathogens in the United States cost $14.1 billion. The difference between these recent estimates could lead to confusion about the total economic burden of foodborne illnesses. This report examines these cost-of-illness estimates with a focus on analyzing the factors that drive differences between them. In this report, "cost of illness" is defined as the sum of treatment costs, the value of time lost to illness, and willingness to pay to prevent death. The studies we discuss estimated cost of illness in slightly different ways.