Recent evidence suggests that human papillomavirus may play a role in the pathogenesis of inverted papilloma, a benign but locally aggressive neoplasm with a high recurrence rate and an association with squamous cell carcinoma. Histologic features of inverted papilloma have not been useful in discriminating lesions at high risk for malignant transformation. We studied archival pathology specimens from 39 patients with inverted papilloma treated at the University of Michigan between 1980 and 1994 using polymerase chain reaction techniques and human papillomavirus L1 and E6 consensus primers. Previously we reported that 63% of these specimens tested positive for human papillomavirus sequences and that presence of human papillomavirus predicted recurrence of inverted papilloma. We used type-specific primer pairs and polymerase chain reaction techniques as well as hybridization with type-specific oligonucleotide probes to determine human papillomavirus type. A significant correlation was observed between the severity of the lesion (dysplasia or carcinoma) and high risk human papillomavirus type ( p < 0.01). All 12 benign inverted papilloma specimens that contained human papillomavirus tested positive for human papillomavirus 6 or 11. Of seven inverted papilloma specimens that exhibited dysplasia, five were human papillomavirus positive, three contained human papillomavirus 6, one contained human papillomavirus 11, and one contained human papillomavirus 18. In each of the three specimens that contained inverted papilloma in association with squamous cell carcinoma, the inverted papilloma portion of the specimen tested positive for a single human papillomavirus type: human papillomavirus 6,11, or 16. Of the four human papillomavirus-positive specimens with squamous cell carcinoma alone (patients who had an inverted papilloma previously resected at the same site), three tested positive for human papillomavirus 16, and 1 was untyped.