This study was conducted in Tan Phu Thanh Village in the Mekong Delta, Vietnam in order to determine the prevalence of Salmonella spp. in the water system, and to reveal the exchange of Salmonella spp. occurring between the water system and livestock in this village. A total of 142 water samples were collected from 40 farms in this village from February to March, 2001. Thirty (21.1%) samples out of the 142 water samples analyzed were positive for Salmonella spp. in culture, based on biochemical tests. A total of 19 different serovars were observed among the 36 isolates from the positive water samples. Serovars Derby (n = 6), O3,10: r :- (n = 4), Anatum (n = 3), Bardo (n = 3), Javiana (n = 3), London (n = 2), Bovismorbificans (n = 2), and Dessau (n = 2) were isolated from more than one water sample. Serovars Derby and Javiana had been observed among the strains isolated from swine in Tan Phu Thanh Village in 2000 (Phan et al., in preparation). Consequently, we attempted to compare these strains of water and animal origins by pulsed-field gel electrophoresis. The difference in the number of bands between the isolates from water and swine was less than 4 in part of the S. Derby and Javiana isolates. These data provide indirect evidence for an exchange of Salmonella between the water system and swine population in this area. Moreover, 3 (6.1%) out of the 49 samples of stored water used for animal watering were positive for Salmonella spp. including the serovar Javiana. Sterilization of stored water is essential to prevent the spread of infection in this area.