The presence of the tet(M) determinant and conjugative transposons related to Tn1545 in urogenital pathogens, Bacteroides ureolyticus (10 strains), Neisseria gonorrhoeae (37 strains) and Ureaplasma urealyticum (81 strains), was studied by PCR analysis and hybridization assay. All tetracycline-resistant strains that hybridized with a probe specific for tet(M) gave the expected fragment when their DNA's were subject to PCR. The tet(M) gene and int-Tn, the gene encoding the protein required for the movement of Tn1545-like transposons, were always found together in tetracycline resistant strains of B. ureolyticus and U. urealyticum. In contrast, int-Tn was not detected in tet(M)-mediated tetracycline-resistant N. gonorrhoeae strains. These data suggest carriage of tet(M) by a Tn1545-like transposon in some tetracycline-resistant B. ureolyticus.