 Carcinoma of the uterine cervix is by far the most prevalent cancer of women in Taiwan and worldwide. In 1994, it ranked the top of female cancer incidence with 3000 new cases annually and claimed nearly 1000 lives. The major cause of this malignant disease is now pointed to the infection of oncogenic types of human papillomavirus HPV. HPV infection is sexually transmitted, affects the immature metaplastic cells of uterine cervix and, in an unknown proportion, results in squamous intraepithelial lesion SIL of differing severity. The natural history of HPV infection is by far elusive. It is not clear how the virus get into the cell, how the immune system respond to it, and how the epithelial cell get transformed. An average estimation holds that about 60 of low grade SIL will regress, 30 will persist, 10 will progress to high grade lesions and less than 1 become invasive lesions. 