The expansion of our knowledge in the realms of pathology, epidemiology, and molecular biology of human papillomaviruses (HPV) has defined them as the major and best understood class of true human tumor viruses. The interaction of the papillomavirus genome with its host cell produces the majority of cytologic abnormalities at which cervical cancer screening is directed. The epidemiologic pattern of HPV infection accounts for the established association of cervical neoplasia with sexual activity. The molecular interactions of the HPV genome with its host cell suggest a plausible mechanism for its carcinogenic action. This presentation will succinctly review current knowledge of HPV biology to facilitate an understanding of the clinical significance of this virus.