Ureaplasma urealyticum and Mycoplasma genitalium are mucosal pathogens which are closely related. They both belong to the family Mycoplasmataceae. The genomes of U. urealyticum and M. genitalium consist of one molecule of circular double-helix DNA. This study was performed to evaluate whether the iga gene of U. urealyticum has high homology with the putative iga gene of M. genitalium, so that this finding might be used as a tool for diagnosing and studying the pathogenesis of U. urealyticum infection. First, cultivation of U. urealyticum in the Ureaplasma media and isolation of the genome were done. Next, verification of the growth of U. urealyticum by amplification of the urease gene of U. urealyticum genome using PCR technique (Kui Teng, 1994). The PCR product was observed by agarose mini gel electrophoresis. DNA primers for amplifying U. urealyticum iga gene were designed based on the nucleotides sequences of putative iga gene M. genitalium. The primers were used for amplifying U. urealyticum iga gene with PCR technique, using the genome of U. urealyticum as the template. The PCR product was observed by agarose mini gel electrophoresis. The iga gene of U. urealyticum was purified by the glassmax method and then labeled with digoxigenin. The digoxigenin labeled iga gene was hybridized to the genome ofU. urealyticum, to find whether the iga gene amplified was derived from the genome ofU. urealyticum. Sequencing the PCR product of the U. urealyticum iga gene was done to evaluate the degree of homology between U. urealyticum iga gene and M. genitalium putative iga gene using “AB1377 DNA sequencer” in the Eijkman Institute. Conclusion of this study: There is 100% homology between a 0,40 kb fragment of U. urealyticum iga gene and a 0,40 kb fragment of M. genitalium putative iga gene.