The following is a report on the frequency of occurrence of Salmonella types observed at the New York Salmonella Center during the first 20 months of its existence, from April 1, 1939, to December 1, 1940. Material.-A complete type culture collection and a set of diagnostic serums were received from Dr. Kauffmann of the International Salmonella Center at the State Serum Institute, Copenhagen, Denmark.1 Additional serums, absorbed factor serums and antigens were prepared. There were obtained from patients of Beth Israel Hospital or submitted from other laboratories for identification 876 cultures. Of these 280 belonged to the Salmonella group, covering 261 human infections in North America. Two cultures of human origin came from abroad, 12 from animals, 1 from foodstuff. There were 3 patients with multiple infections from whom 7 strains were isolated. Technic.-The serological Salmonella types were identified according to the International or Kauffmann-White schema.2 Ordinarily slide agglutinations were sufficient for diagnosis. O serums were used in dilutions 1:5 or 1:10 according to their titer (1:320 or 1:640), H serums with titers 1:1600 and higher were used in dilutions of 1:50 or 1:100. If only one phase of the H antigen was demonstrable, single colonies were produc d on thick-layered, moist agar plates. Tests were made for the presence of Vi antigen, because it would explain lack of O agglutination. Autoagglutinable or O inagglutinable cultures were subcultured in broth containing active guinea pig serum to suppress the rough phase. Nonmotile strains often became motile after they were cultured in broth at room temperature for several days. Occurrence of the different types in man in North America.-In the following report the distribution of types derived mainly from human infections in the United States and Canada, is compared with the findings of Edwards,3 among North American animals, and of Hormaeche4 among children in South America. Group A.-This group is represented by only one type: S. paratyphi A. It occurs rather rarely in the Western hemisphere and was encountered neither by Edwards nor by Hormaeche. We received one strain which exhibited both somatic antigens I and II. Group B.-Up to the present many of the 22 types which form group B were found only in animals. We diagnosed the following 5 types: S. paratyphi B, S. typhi murium (other names: B. aertrycke, B. pestis caviae, B. paratyphi B type Breslau), S. chester, S. derby and S. abortus equi. All these types were isolated from man; S. typhi murium was also isolated from puppies, mice and parrakeets. Of these types, S. paratyphi B and S. chester were not represented in Edwards' material, while he observed in Received for publication, January 16, 1941. Aided by a grant from the Committee on Scientific Research of the American Medical As-