Human papilloma viruses (HPVs) can be classified as either high risk or low risk according to their association with cancer. HPV16 and HPV18 are the most common of the high-risk group while HPV6 and HPV11 are among the low risk types. Approximately 90% of cervical cancers contain HPV DNA of the high-risk types. Mutational analysis has shown that the E6 and E7 genes of the high-risk HPVs are necessary and sufficient for HPV transforming function. The antibody reacts very strongly with formalin-fixed, paraffin-embedded tissues containing HPV-16, -18 or -33.