Salmonellae are commonly isolated from dogs. The number of dogs infected with Salmonella spp. is surprisingly high and greater than the incidence of clinical disease would suggest. Salmonellosis is common in greyhound kennels. Morbidity can approach 100% in puppies and the mortality ranges to nearly 40%. To date, there has been little effort to evaluate the feasibility of a vaccine for control of this disease in dogs. In the studies described here, an attenuated strain of Salmonella enterica serovar Typhimurium (Se Typhimurium), chi4127, was capable of establishing a limited infection in dogs. The chi4127-attenuated salmonellae efficiently stimulated protective immune responses in serotype homologous, direct, oral challenge experiments. Morbidity in the wild-type-challenged dogs was 8.3% in immunized dogs but 100% in the non-vaccinated controls. In (9/12) control dogs, the disease involved both gastrointestinal and respiratory tracts with high fever (>40.2 degrees C) that persisted through 5 days after challenge. Serum IgG response against S. typhimurium lipopolysaccharide (LPS) significantly increased (P<0.01) in vaccinated dogs and in non-vaccinated dogs after challenge. The non-vaccinated dogs had 3 to 4 logs higher numbers of Se Typhimurium in splenic and hepatic tissue than did the vaccinated dogs. This particular attenuated strain has potential for use as a vaccine for canine salmonellosis.