In veterinary literature a distinction is usually made among infections caused by the two nonmotile host-adapted serovars of Salmonella, the arizonae group of salmonellae, which cause arizonosis, and the remainder of the salmonellae, which cause salmonellosis and paratyphoid infection. Salmonellosis is one of the most frequent foodborne infections in human beings, and contaminated poultry products are major sources of infection. The environment is often extensively contaminated by salmonellae excreted by acutely or persistently infected animals. Poultry carcasses and parts are frequently contaminated by salmonellae. Diagnosis requires isolation and identification of the etiologic salmonellae, preferably with identification of specific serovars. In addition to programs to control salmonellae in poultry flocks, several programs have been initiated to prevent egg-borne transmission.