Causality requires a judgment based on scientific evidence from human and experimental studies, as strict causality studies are often not appropriate in humans. Evidence linking certain human papillomavirus (HPV) genotypes to cervical carcinoma is extensive and compelling. More than two decades of research has led to the fulfillment of criteria, as proposed by Hill, to establish a causal link between high risk HPV infection and cervical cancer (Table 1). HPV DNA was first isolated from biopsies of cervical cancer more than 30 years ago (1, 2). HPV DNA is detected in 99.7% of cervical carcinomas worldwide. The evidence overwhelmingly demonstrates that persistent high risk HPV infection is a necessary but not sufficient cause of this cancer (3).