Orogenital transmission has been suggested for several viruses, e.g. herpes simplex virus‐1 and ‐2 (HS‐1 and HSV‐2), Epstein‐Barr virus (EBV), cytomegalovirus (CMV), human herpesvirus‐8 (HHV‐8), human papillomavirus (HPV) and HIV. Most studies have focused on HIV, HSV and HPV. Unprotected orogenital contact, especially receptive oral intercourse, is associated with greater risk of HIV transmission than previously thought. Factors potentially associated with increased risk of HIV transmission through oral sex include poor oral health, the salivary anti‐HIV properties such as peroxidases and thrombospondin‐1, the local and systemic immunological responses, concomitant sexually transmitted infections, ejaculation in the mouth, local mucosal integrity, and the level of infectious HIV present at the oral mucosa. The probability of per act transmission in oral intercourse with ejaculation is 0.04%. HSV‐2 has been regarded as a sexually transmitted virus while HSV‐1 is causing primary herpetic gingivo‐stomatitis, muco‐cutaneous oro‐facial disease and ocular disease. Also HSV‐2 might be detected occasionally in oro‐facial area. Recent data on young women with a primary genital infection indicate that HSV‐1 is much more frequent than HSV‐2. Oro‐genital route of transmission is more common than expected in genital HSV‐1 infections. EBV is a tumorigenic herpes virus that is carried as a persistent infection by more than 90% of adults. Most persistently infected people produce EBV in their saliva, and transmission is through close contact. There is a significant association between sexual intercourse and EBV seropositivity, increasing with numbers of sex partners. Because EBV has been found in genital secretions from healthy seropositive men and women, direct spread of virus during sexual intercourse is possible. Today, 106 HPV types have been sequenced of which almost 40 have been detected also in oral mucosa, causing benign epithelial lesions (papillomas, condylomas, warts and focal epithelial hyperplasia, or FEH). Recent meta‐analyses of the case‐control studies have confirmed HPV as an independent risk factor for oral SCC with odds ratios (OR) 3.7 to 5.4. HPV16 is the overwhelmingly most frequent type. HPV has been regarded as a sexually transmitted disease but this view is challenged by frequent detection of HPV in children. Unlike in genital tract, natural history of oral HPV infection is poorly studied. As part of the Finnish HPV Family Study we evaluated natural history of oral HPV in within family members. The detection rate of HR HPVs varied from 15% to 27%. Our results indicate that natural history of HPV infection in oral mucosa mimics that of genital HPV infections. Oral sex had no association to oral HPV infection, but a persistent oral HPV infection of the spouse increased the risk of persistent oral HPV infection in the other spouse 10‐fold.