Although human papillomavirus (HPV), a sexually transmitted virus, is established as a necessary cause for more than 95% of cervical carcinomas, the association with oral squamous cell carcinoma is less well delineated. The purpose of this study was to determine the frequency and types of HPV in squamous cells of a group of patients with newly diagnosed oral or pharyngeal cancer (n = 93) compared with an age- and gender-frequency-matched control group of patients with no history of oral cancer (n = 205). HPV was evaluated from a mouth rinse collection of cells in the oral cavity and tested by 32P-labeled HPV generic probes and DNA sequencing for HPV types. HPV was identified in 15% of the oral cancer cases but in fewer than 5% of the controls (P < .05). The risk of cancer associated with HPV infection was independent of tobacco and alcohol use (adjusted odds ratio [OR] = 3.70; 95% confidence interval [CI]: 1.47-9.32; P < .05). HPV types included similar and other types not identified previously in the genital tract. There was no statistically significant increased risk of cancer among former tobacco users (former vs. never users: adjusted OR = 0.67, 95% CI: 0.31-1.44, P < .05), but the risk was significantly increased for current users (current vs. never: adjusted OR = 2.63; 95% CI: 1.22-5.71; P < .05). Likewise, former alcohol users were not at increased risk of disease (former vs. never: adjusted OR = 1.78; 95% CI: 0.87-3.67), whereas current alcohol users were (current vs. never: adjusted OR = 2.57; 95% CI: 1.22-5.42; P < .05). HPV-related genital lesions (14.3% vs. 10.6%), oral-genital sexual behavior (42.4% vs. 45.2%), and number (11 or more) of sexual partners (23% v. 17%) were not significantly different between cases and controls. These data suggest that in addition to tobacco and alcohol, HPV plays a role in the development of oral cancer.