We studied 40 formalin-fixed, paraffin-embedded esophageal squamous cell carcinomas from a high risk region for this tumor for the presence of human papillomavirus (HPV) DNA by the polymerase chain reaction (PCR). We used two general consensus primers from a highly conserved E1 region of HPV types 6, 11, 16, and 18. Human papillomavirus DNA was detected in 60% (24 of 40) of the cases without relation to the tumor grade. Two lymph node metastases had the same HPV types as the primary tumor. Human papillomavirus types were determined in the 24 HPV-positive cases by Southern blot analysis of amplified DNA. Human papillomavirus type 6 was detected in 50% (12 of 24) of the cases, HPV type 16 in 8% (two of 24), and HPV types 6 and 16 in 17% (four of 24); in 25% (six of 24) of the cases the type was unknown. Human papillomavirus types 11 and 18 were not detected. Esophageal mucosa adjacent to the tumor was studied for morphological changes of HPV effect in 27 cases. Adjacent esophageal mucosa in 16 HPV-positive tumors showed statistically significant (P < .05) koilocytosis in six cases. Papillomatosis was the next most frequent finding in four cases. This study supports the role of HPV in the causation of esophageal squamous cell carcinomas, especially in high risk regions for this tumor.