AbstractSalmonellosis affects more people and more animals than any other single disease. It is one of the most important public health and animal health problems. Salmonellosis may vary in severity from inapparent infections to acute disease which may be fatal to the very young, the old, or the debilitated individual. It is estimated that there are 2 million persons infected each year in the United States. During the past quarter of a century, except for typhoid fever, reported salmonella infections in man in the United States have increased from 504 in 1942 to 20,867 bacteriologically proven infections in 1965. It is impossible to determine how much of the marked increase in reported human salmonellosis is due to actual increase in incidence of infections and how much is due to improved reporting. Methodology has improved during this period, but it is believed that wider application of known methods and more thorough epidemiological investigation of outbreaks have contributed most information about the occurrence and distribution of salmonellae.