Our understanding of the biology of papillomaviruses has increased dramatically over the past 25 years. Before then, the lack of a facile tissue culture system had left this virus family behind the other "DNA tumor viruses," such as SV40 and murine polyomavirus. However, with the advent of molecular cloning and other new techniques, coupled with the pivotal stimulus given by connecting HPV infection and cervical cancer, the field has flourished. This...