High-risk human papillomavirus (HPV) infection is a risk factor for head and neck cancer. In this study, Dr. Brockton and his colleagues will investigate the effect of HPV infection on the expression of endogenous markers of hypoxia (EMH) by exploiting an existing retrospective cohort of tumours assembled in tumour microarrays. Because HPV infection may effect the expression of EMH, failure to stratify tumours by HPV status may account for the disappointing predictive value of EMH.