Human papillomavirus (HPV) infection of the mouth and oropharynx can be acquired by a variety of sexual and social forms of transmission. HPV-16 genotype is present in many oral and oropharyngeal squamous cell carcinomata. It has an essential aetiologic role in the development of oropharyngeal squamous cell carcinoma in a subset of subjects who are typically younger, are more engaged with high-risk sexual behaviour, have higher HPV-16 serum antibody titer, use less tobacco and have better survival rates than in subjects with HPV-cytonegative oropharyngeal squamous cell carcinoma. In this subset of subjects the HPV-cytopositive carcinomatous cells have a distinct molecular profile. In contrast to HPV-cytopositive oropharyngeal squamous cell carcinoma, the causal association between HPV-16 and other high-risk HPV genotypes and squamous cell carcinoma of the oral mucosa is weak, and the nature of the association is unclear. It is likely that routine administration of HPV vaccination against high-risk HPV genotypes before the start of sexual activity will bring about a reduction in the incidence of HPV-mediated oral and oropharyngeal squamous cell carcinoma. This article focuses on aspects of HPV infection of the mouth and the oropharynx with emphasis on the link between HPV and squamous cell carcinoma, and on the limitations of the available diagnostic tests in identifying a cause-and-effect relationship of HPV with squamous cell carcinoma of the mouth and oropharynx.