1. Salmonella incidents in Northern Ireland from 1951–58 are compared with the published findings in England and Wales.2. Caecal swabs from 489 pigs killed in two bacon factories showed a salmonella isolation rate of 2%.3. Salmonella organisms were isolated from twenty-three out of 100 samples of caecal faeces and from only six of 100 caecal swabs taken from the same animals. Three per cent of meat samples from these pigs and 70% of sausage samples from this meat contained Salmonellae.4. Rectal swabs from 162 pigs on five farms producing infected pigs showed Salmonellae in 9% of those examined.5. Twenty-four per cent of pig-meal samples taken on these farms contained Salmonellae, and the same salmonella types were found in the meal at the mill and in fish meal and bone meal before mixing.6. It is probable that some salmonella types pass from feedingstuffs through pigs to human food and cause human infections.We should like to express our thanks to Dr Joan Taylor of the Salmonella Reference Laboratory, Colindale, for typing many of the Salmonellae; to Mr J. Stuart of the Veterinary Division, Ministry of Agriculture, Northern Ireland, for help in sampling at an abattoir and on the farms; to the staff of the Northern Ireland Hospitals Authority, Central Laboratory, for technical assistance; to Mr J. Patton and Dr D. Luke for much help and advice at many stages of this inquiry; to Miss A. McCann for the secretarial work; to the Northern Ireland Hospitals Authority for a grant towards the expenses in 1958; and to our colleagues in the Local Authorities, General Practice, on the farms and in the factories who were always most helpful and co-operative.