1. The mesenteric lymph nodes and faeces of pigs, cattle, sheep, dogs and cats and the intestinal wall and other organs of chickens in Essex, England, have been examined for salmonellae. These animals were either healthy or were not suffering from clinical salmonella infection.

2. Salmonellae were isolated from the mesenteric lymph nodes of sixty (12%) of 500 pigs, nine (4·5%) of 200 dogs, five (2·5%) of 200 cats and none of 200 cattle and 100 sheep. None was found in the chickens.

3. One (0·5%) of the cats and one (0·5%) of the dogs and six (1·2%) of an additional 500 healthy pigs were excreting salmonellae in their faeces.

4. Of the seventeen serotypes found in pigs, Salm. typhi-murium, Salm. anatum and Salm. cholerae-suis occurred most frequently.

5. All strains of Salm. cholerae-suis were isolated in brilliant green MacConkey broth; selenite broth was unsuitable for this purpose.

6. Despite the high isolation rate from pigs, clinical salmonella infection was diagnosed relatively infrequently at this laboratory. Salm. cholerae-suis was isolated from only one of seventeen epidemiologically unrelated cases of necrotic enteritis in pigs.

7. The results are discussed from the public health and agricultural view points with particular regard to the part infected feedingstuffs may play in causing salmonella infection in animals.

The expenses of the investigation were, in part, defrayed by grants from the Agricultural Research Council, whose help I gratefully acknowledge.

I am grateful to Mr A. J. Harman and Miss Linda Kelly for their capable technical help and to Dr K. C. Sellers for useful suggestions made during the course of this work. I am also indebted to Dr Joan Taylor for typing all the salmonella cultures and to Mr L. G. Smart for collecting the lymph nodes from the cattle, sheep and pigs.