Fifty cervical adenocarcinomas and 50 squamous cell carcinomas from age-matched patients were examined for human papillomavirus (HPV) types 16 and 18. The polymerase chain reaction was used to examine formalin-fixed, paraffin-embedded carcinoma tissues for 120 and 113 bp sequences, respectively, of the highly conserved E6/E7 regions of the viral genomes. HPV type 16 was detected more often in squamous cell carcinomas than in adenocarcinomas (60% vs 18%, P less than 0.001). Conversely, HPV type 18 was detected significantly more often in adenocarcinoma tissues (52% vs 12% in squamous cell carcinomas, P less than 0.001). These differences may reflect the fact that different virus receptors exist in cervical cells with different morphologic potential, or they may indicate that the specific HPV infection actually plays a role in directing carcinogenesis.