During the last 15 years, strong evidences have shown that some particular HPVs are involved etiologically in HNCs, especially in the oropharynx. However, this cancer etiology is multifactorial and tobacco and alcohol consumption also play an important role on it. In order to estimate the crude and adjusted HPV prevalence in HNCs, a study, which recruited HNC cases from 1990 to 2012 worldwide using different biological markers, as the presence of the virus DNA, E6*I mRNA, and p16INK4a expression, was conducted at ICO (Castellsagué X., et al., 2016). The aims of this MFP were: 1) To determine the variables associated to HPV infection in HNCs using unconditional logistic regression analysis with in international cross-sectional study. 2) To conduct a time series analysis using Bayesian methodology to evaluate how HPV prevalence in oropharyngeal cancers has evolved from 1990 until 2014 in Spain. 2.1) From a statistical point of view, we compared the results obtained with frequentist statistics to evaluate their benefits and inconveniences.