Classical microbiological techniques used in the detection and identification of Salmonella spp. in foods, drinking water and clinical samples are relatively lengthy. Immunoassays, on the other hand, have the major disadvantage of often generating false positives and false negatives. Recombinant DNA technology offers more efficient alternatives to the detection of a specific organism by employing cloned DNA sequences unique to the organism. Demonstration of a presence of complementary sequences among a heterogeneous population of molecules of DNA isolated from bacteria can be made by using a DNA-DNA hybridization technique. We have obtained a fragment of DNA from Salmonella typhimurium chromosomal DNA, cloned it in Escherichia coli plasmid and tested it in colony hybridization tests with 57 strains of Salmonella and other enterobacteriaceae. In all tests, the fragment was found to be Salmonella-specific in that it gave a positive reaction with all strains of Salmonella tested and was negative when tested against other Enterobacteriaceae.