All 38 isolates of Salmonella enteritidis phage type (PT) 4 from chickens and 86 of 89 isolates from human patients were resistant to nitrofurantoin. Resistance to other agents was rare. Thirteen of 16 isolates of S. enteritidis other than PT4 were nitrofurantoin-resistant, and resistance to other agents was slightly more common than with isolates of PT4. Only one third of 83 isolates of other salmonella serotypes were nitrofurantoin-resistant, but resistance to other agents was more common and some isolates were multiply resistant. There was generally cross-resistance between nitrofurantoin and furazolidone although there were discrepancies with isolates that had MICs close to the breakpoint. It may be that use of nitrofurans in the poultry industry has selected for colonization and infection with S. enteritidis PT4. This could explain the prevalence of the organism in poultry and in human enteric infection in the United Kingdom.