Human papillomavirus (HPV) infects epithelial cells in the skin or mucous membrane, causing asymptomatic infection or benign lesions, squamous cell carcinoma or premalignant lesions. The natural history of HPV infection is best known in the female genital area. Research interest in oral infections has increased with the availability of commercial HPV vaccines. At the moment there is not enough information as to which HPV types infect the oral mucosa or on the natural history of HPV infections. The most common HPV genotype found in oral mucosa is HPV16. Asymptomatic oral HPV infections and infections with multiple types occur more frequently in immunocompromised patients; in addition, papillomas/condylomas caused by HPV take longer to heal. Rates of anal and cervical cancers caused by HPV have increased in HIV-infected patients, while there are only single case reports of oral cancer in these patients. Organ transplant patients also have more oral warts, which heal more slowly than those in healthy persons. It is likely that HPV vaccines also prevent oral HPV infections. However, the effect of the vaccine is affected by timing: prophylactic vaccine must be given before the first HPV infection. It is therefore likely that many immunocompromised patients have already been infected by HPV.