The provision of supplementary food for wild birds in gardens during the winter months is common in the UK, but it is possible that it may precipitate infectious diseases in the birds. This paper describes the results of postmortem examinations of 116 wild finches carried out over a period of four years. The two commonest causes of death in areas where high mortality had been reported were infections with the bacteria Salmonella typhimurium DT40 and Escherichia coli O86. Coccidia of the genera Atoxoplasma or Isospora were found in several of the birds but were considered to be incidental. Megabacteria were also identified in some of the birds, for the first time in flocks of wild birds in the UK, but they were not considered to be significant.