Clinical manifestations of sexually transmitted infections (STI) more frequently localized in genital area. Although, these infections can also be transmitted through oral genital or oral anal sexual practices in men and women. Thereby, various clinical symptoms and manifestations of STI in oral cavity can be undetected by specialist and lead to diagnostic errors. Erosive ulcerative and nodular changes on lips, burning on tongue, plaque, ulceration, leukoplakia, tickle, taste disorder, sore throat while swallowing, difficult speech, hoarseness, gingivitis and other changes in mucous membranes of oral cavity have different causes. Nevertheless, all above mentioned clinical symptoms also can be caused by STI. If specialist does not consider the possibility of STI localization in oral cavity, then, as a rule, focused sexual anamnesis is not collected. A significant delay in diagnosis verification and adequate therapy prescription, that could prevent the further spread of STI in population, is a probable consequence. Patients, in their turn, do not have appropriate openness and specific vocabulary to describe risky sexual behavior. The authors discuss the possible relationship between oral cavity microbiome and risk of STI contamination in the review article. As a rule, the symptoms and clinical manifestations of STI in oral cavity are not specific or may be absent. Laboratory diagnosis is essential for the STI verification. The authors note that understanding the clinical epidemiological features of STI is important for practitioners. The authors pay particular attention to diseases which localized in oropharyngeal region such as syphilis, gonorrhea, chlamydial infection, herpes, candidiasis, HPV-related diseases, HIV infection and others. The article is illustrated by clinical reports from authors’ personal practice.