Major progress has been made to control cervical cancer in the United States and Europe using screening programs, although it remains a major cause of morbidity and mortality in the developing world. The association between cervical cancer and a sexually transmissible etiologic agent was hypothesized long before identification of human papillomaviruses (HPV) as agents that infected the genital tract. HPVs are among the most common sexually transmitted agents and have been shown to induce several squamous anogenital cancers, including squamous cell cancer of the cervix. After an etiologic role for HPV was identified in cervical cancer and CIN, efforts to understand the molecular biology of HPV were greatly expanded, enhanced by the advent of deoxyribonucleic acid (DNA) probes to identify HPV infection. Recent research has focused on specific types of HPV in relation to other recognized risk factors in the pathogenesis of CIN and invasive cervical cancer.