A large outbreak of Salmonella Typhimurium occurred in Gideon, Missouri. The investigation implicated the community's unchlorinated water supply. The Salmonella was unusual in that it did not ferment dulcitol. Salmonella Typhimurium was found in water samples taked from fire hydrants and from a water storage tank. Even though a boil water order had been issued in response to the outbreak, approximately one third of the population admitted to drinking the water after the boil water order was issued.