 The Presidents Cancer Advisory Board and the Centers for Disease Control have called for renewed efforts in promoting vaccination for Human Papillomavirus HPV, including vaccination for adolescent boys, because the uptake of this new vaccine remains alarmingly low. Currently, less than 15 of adolescent boys have received the HPV vaccine; thus, most of this population remains at risk for oropharyngeal, anal, and penile cancers. Many parents remain unconvinced of the safety and effectiveness of HPV vaccines, so effective and accessible messaging to improve decision-making on this vaccine is needed. Parents of adolescent boys also have different concerns about HPV vaccination than for adolescent girls, creating a need for unique health communication interventions to promote vaccine uptake among boys. Interventions also need to address the unique challenges of minority populations and populations for whom English is not the first language. A novel digital intervention will be produced and evaluated for its ability to improve HPV vaccine outcomes. Specifically, a mobile responsive web application mobile web app will be created that performs similar to a mobile app but runs on a variety of computing platforms from personal desktop and laptop computers to the latest smart phones and tablet computers. Mobile web app content will be targeted to parents and adolescent boys aged 11-13 years living in New Mexico, a majority-minority population with large proportions of Hispanics, Whites, and Native Americans. The specific aims are to: 1 carefully and systematically develop a mobile web app BoyVac for smart phones, tablet computers, and personal computers that will utilize Diffusion of Innovations principles to provide targeted information concerning HPV vaccine adoption to adolescent males and their parents, particularly minority adolescents and parents; 2 implement a comprehensive and rigorous test of the impact of the BoyVac mobile web app intervention on HPV vaccine adoption outcomes via a randomized efficacy trial BoyVac v. usual and customary care; and 3 examine the dose-response relationships between mobile web app usage and vaccine outcomes within a components analysis. A group-randomized pretest-posttest controlled design will be implemented, recruiting 1800 pairs of parents and adolescent boys from 30 pediatric clinics n60 parents and boys per clinic affiliated with the Envision New Mexico, a best practices program at the University of New Mexico Health Sciences Centers Department of Pediatrics. Parents will be surveyed at baseline, a 3-month follow-up, and a 9-month follow-up and records HPV vaccination adoption for the boys will be obtained from the clinics medical records at the 9-month follow-up. Analyses will test the hypotheses that 1 more 11-13 year old boys in the intervention group BoyVac mobile web app will adopt the HPV vaccine than boys in the usual and customary care comparison group and 2 adoption of HPV vaccine will be mediated by improvements in theoretical mediators among parents in the intervention compared to the usual and customary care comparison group. 