Human papillomaviruses are present in virtually all cervical cancers and cancer precursors. Understanding the epithelial virology of this group of viruses has greatly influenced current concepts of cervical carcinogenesis, has provided a framework for understanding the biologic basis of many diagnostic criteria, and has led to revised classification schemes, diagnostic testing, and modifications in clinical management. This paper briefly reviews virologic concepts supporting the pathogenetic role of these viruses in cervical neoplasia.