Mycoplasmas, cell wall-less bacteria of class Mollicutes, are among the smallest self-replicating organisms known and reside ubiquitously at the cell membrane or internalized into the cell. They mimic viruses in many of their activities and further they may have oncogenic activity. The oncogenic potential of mycoplasmas was only recently realized when they were shown to cause chromosomal changes and in vitro cell transformations through gradual progressive chromosomal loss and translocations. The association between these organisms and human cancers has been evaluated and actually mycoplasmas were detected in 50% of gastric cancers. In gynecologic cancer, one study demonstrated a 59.3% prevalence rate of mycoplasmas in malignant ovarian tumors but the explanations for the association between the organisms and ovarian cancer might be somewhat confusing, at least in part, due to absence of normal control. The present objective was to determine the presence of mycoplasma DNA in ovarian cancer tissues and normal ovary in Korea. Fresh frozen tissue samples stored at -72 degrees C were used for mycoplasma DNA assay. The study materials comprised twenty-nine human ovarian cancer tissues and ten normal ovarian tissues. After extraction of DNA, the combined PCR-ELISA(polymerase chain reaction and enzyme linked immunosorbent assay) procedure was performed with consensus primers targeting for 15 species of mycoplasmas and acholeplasmas together with negative and positive controls, which was known as very sensitive method. The results showed mycoplasma DNA were present in none of normal ovarian tissue and in 13.8%(4 of 29) of the ovarian cancer specimens, which is much lower than that of the previousstudy. Three positive cases showed very strong reactivities, but there was no significant correlation between presence of mycoplasma DNA and the clinicopathological characteristics of the patients. These results suggest that mycoplasma can not be the contributor in the mechanism of carcinogenesis in the most of ovarian cancers in Korea, but the association between mycoplasma and ovarian cancer is worth to be investigated.