Infection with HPV-16 is strongly associated with squamous cell carcinoma of the oropharynx and is detected in approximately 50% of these tumors. In a small study of patients with squamous carcinomas of the head and neck as well as studies of women with cervical cancer, detection of HPV-16 DNA in peripheral blood appears to be a strong predictor of tumor recurrence. Larger studies from several institutions have utilized a similar concept with significant success in patients with nasopharyngeal carcinoma Furthermore, viral DNA load can be an earlier indicator of recurrence than clinical exam or imaging. It is our hypothesis that the presence of HPV-16 in peripheral blood of oropharyngeal carcinoma patients will be an early indicator of recurrent disease and in particular distant metastatic disease. To test this hypothesis, as a parallel collaborative project with MDACC, USA and Hospital do cancer, Brazil, we will recruit 63 patients (in one year) with oropharyngeal cancer and determine via real-time PCR whether the patients have detectable HPV-16 DNA in their sera both before and after treatment. Follow up will be determined by the treating clinicians. Blood will be obtained approximately 6 weeks after completion of radiotherapy and approximately every 6 months for 3 years.