Schneiderian papillomas are uncommon benign tumors of the sinonasal area. They are prone to local aggressiveness and recurrence, and some undergo malignant progression. We analyzed specimens obtained from 67 Chinese patients who had presented to the ENT department of a regional hospital with biopsy-proven schneiderian papilloma. Seven of these patients had either synchronous or metachronous carcinoma, 1 of whom had pure carcinoma in situ. For each case, we documented the morphology, immunohistochemical expression of tumor suppressor genes p53 and p16, and any association with human papillomavirus (HPV) infection as detected by either polymerase chain reaction or in situ hybridization techniques. We found that severe dysplasia and p53 positivity were strongly associated with malignant progression. Association with HPV was demonstrated in 22 of the 67 patients (33%); the association was strongest among patients with exophytic papillomas and carcinomas. The effect of HPV in papilloma oncogenesis probably begins during the early phase, while other factors are responsible for progression to carcinoma. We conclude that p53-positive, dysplastic schneiderian papillomas warrant aggressive surgical treatment.