Technical Abstract: House flies (Musca domestica) released into rooms containing hens challenged with Salmonella enterica serovar Enteritidis (S. enteritidis) rapidly became contaminated with S. enteritidis. Forty to 50% of the flies were contaminated at 48 hours which increased to 50-70% at 4 and 7 days post exposure and then decreased to 30% at day 15. Initial attempts at recovering surface organisms for culture using a PBS rinse was largely unsuccessful while culture of internal contents readily recovered S. enteritidis. However, when 0.5% detergent was incorporated into the rinse, high bacterial recoveries were observed from both external and internal culture regimes, indicating equal distribution of the organism on and in the fly and a tighter interaction of the organism with the host than previously thought. S. enteritidis was isolated routinely from the fly gut, on rare occasion from the crop, and never from the salivary gland. Feeding contaminated flies to hens resulted in gut colonization of a third of the birds but release of contaminated flies in a room containing previously unchallenged hens failed to result in colonization of any of the subject birds. These results indicate that flies exposed to an environment containing S. enteritidis can become colonized with the organism and might serve as a source of S. enteritidis transmission within a flock situation.