One of the factors associated with an increased risk of HPV-related malignant transformation may be bacterial and/or viral infections. The aim of our study was to examine whether the presence of infectious agents commonly detected in the genitourinary tract such as herpesviruses (HSV, CMV), and ureaplasmas (Ureaplasma urealyticum, Ureaplasma parvum) may lead to alterations in the expression of the HPV-16 E6 oncogene. Quantitative RT-PCR analysis was used to assess the level of HPV-16 E6 mRNA expression in SiHa cells. The presence of HSV-1 or HSV-2 in SiHa cells caused a 1.5-fold increase in HPV-16 E6 mRNA expression as compared with non-inoculated SiHa cells. Ureaplasma urealyticum presence but not Ureaplasma parvum stimulated the expression of HPV-16 E6 resulting in a nearly five-fold (4.8) up-regulated E6 mRNA level in SiHa cells. Our study is the first to suggest that infection of Ureaplasma urealyticum in an urogenital tract could increase the risk of cervical cancer by overexpression of the HPV E6 oncogene.