Human papillomaviruses cause the most common sexually transmitted infection in the world and are responsible for nearly all cases of cervical cancer. Genital human papillomavirus infection can be divided into low-risk infections (causing genital warts) and high-risk infections (causing cervical intraepithelial neoplasia, and cervical and other cancers). Exposure to human papilloma- virus typically produces a sexually transmitted infection that may progress to a clinically apparent process, such as genital warts and cervical intraepithelial neoplasia lesions of the lower genital tract. Although most human papillomavirus infections resolve spontaneously within two years, some high-risk infections persist and are considered cancer precursors. Risk factors for persistent infection include multiple sex partners, sex at an early age, history of sexually transmitted infections, and smoking. Condom use is only partially protective against human papillomavirus infection. The two human papillomavirus vaccines are most effective if given to girls before the onset of sexual activity.