HPV-16 is a non-enveloped DNA virus that causes warts, cervical carcinomas, and anogenital tumours. Cervical cancer is the third most common cancer among women worldwide, and it is the most common cancer among women in developing countries. To develop new anti-viral therapies, it will be important to understand HPV entry into ist host cells. HPV-16 enters cells by endocytosis, and it seems likely that it penetrates into the cytosol from classical endosomes. Replication occurs in the nucleus.