Most nasopharyngeal carcinomas (NPCs) are of the nonkeratinizing or undifferentiated types, which are consistently associated with Epstein-Barr virus (EBV). The smaller group of highly differentiated, keratinizing NPCs seems to be only infrequently associated with EBV. In order to examine whether these rare tumors were related to another oncogenic virus, the authors used the polymerase chain reaction to examine paraffin-embedded sections of 15 keratinizing NPCs for human papillomavirus (HPV) types 6, 11, 16, and 18 genomic sequences. HPV DNA was found in 4 tumors (1 HPV-11-positive, and 3 HPV-16-positive tumors). None of 23 undifferentiated or nonkeratinizing NPCs harbored HPV DNA. The putatively oncogenic HPV type 16 may thus be involved in the carcinogenesis of some EBV-negative keratinizing squamous cell nasopharyngeal carcinomas.