Field and collection isolates of Salmonella abortusovis carry one IS200 element in a distinct chromosome location. IS200 is not found in the corresponding region of the chromosome of other Salmonella serovars. Sequencing of the boundaries of the S. abortusovis-specific IS200 insertion permitted the design of primers for the amplification of this IS200 element by PCR. Isolates of S. abortusovis are identified by the amplification of a DNA fragment of about 900 bp or larger. PCR amplification of DNA from salmonellae other than S. abortusovis yields either a fragment of about 200 bp or no product. The high specificity of the assay is confirmed by the absence of cross-reactivity with the following templates: (i) sheep DNA, (ii) DNAs from abortion-causing agents other than S. abortusovis, and (iii) DNAs from microorganisms that do not cause abortion but are common in flocks.