To　investigate　the　association　between　human　papillomavirus　(HPV)　infection　and　esophageal　cancer,　genomic　DNA　was　isolated　from　189　samples　obtained　from　patients　with　esophageal　carcinoma,　and　HPV　DNA　was　identified　using　the　polymerase　chain　reaction　(PCR)　with　the　following　specific　primers:　My09/11　for　HPV　L1　and　HPV18　E6　for　HPV18.　The　HPV18　gene　products　were　sequenced　to　identify　the　HPV　genotype　and　the　HPV18　integration　site　was　verified　using　PCR　amplification　of　papillomavirus　oncogene　transcripts.　HPV18　oncogene　transcript　products　were　ligated　into　a　pMD-18T　plasmid　vector　and　sequenced　to　confirm　the　physical　location　of　HPV18　integration.　Of　the　189　samples,　168　were　positive　for　HPV,　of　which　33　were　positive　for　HPV18.　The　sequencing　analysis　identified　two　HPV18　E6-positive　samples　containing　one　mutation　and　two　samples　containing　two　mutations　in　the　viral　DNA.　In　total　similar　to　600　bp　of　the　HPV18　oncogene　transcript　was　detected　in　three　esophageal　cancer　samples.　Sequence　analysis　revealed　that,　in　two　patients,　the　HPV18　infection　was　integrated　into　human　chromosome　5,　whereas　in　the　remaining　sample　the　virus　was　integrated　into　human　chromosome　2.　The　high　prevalence　of　HPV18　infection　suggested　that　HPV18　infection　is　a　pathogenic　factor　in　esophageal　carcinoma　progression.　The　integration　of　HPV18　DNA　into　the　host　cell　genome　suggests　that　persistent　HPV　infection　has　a　role　in　esophageal　epithelial　cell　malignant　transformation　and　carcinogenesis.