Epidemiology of head and neck cancers is currently intensively studied topic. Recent shift in the age of incidence towards younger population is generally attributed to growing proportion of head and neck cancers caused by human papillomavirus - sexually transmitted virus which causes asymptomatic, but sometimes persisting infection that can lead to malignant transformation of the infected tissue. Significance of the topic lies mainly in the prognostic ad- vantage of patients with virally induced head and cancers and preventabil- ity of infections with human papillomavirus. First aim of this thesis is to demonstrate epidemiological trends of head and neck cancers in the Czech Republic, with the focus on change of age-specific incidence and mortality in the last three decades. Second aim of this thesis is to identify risk factors of oral infections with human papillomaviruses and head and neck cancer in a case-control and cross-sectional study of a hospital-based cohort. 1