In 2009, the United States approved quadrivalent HPV vaccine for males 9-26 years old, but data on vaccine uptake are lacking. We determined HPV vaccine uptake among adolescent males, as well as stage of adoption and vaccine acceptability to parents and their sons. A national sample of parents of adolescent males ages 11-17 years (n=547) and their sons (n=421) completed online surveys during August and September 2010. Analyses used multivariate linear regression. Few sons (2%) had received any doses of HPV vaccine, and most parents and sons were unaware the vaccine can be given to males. Parents with unvaccinated sons were moderately willing to get their sons free HPV vaccine (mean=3.37, SD=1.21, possible range 1-5). Parents were more willing to get their sons vaccinated if they perceived higher levels of HPV vaccine effectiveness (β=0.20) or if they anticipated higher regret about their sons not getting vaccinated and later developing an HPV infection (β=0.32). Vaccine acceptability was also modest among unvaccinated sons (mean=2.98, SD=1.13, possible range 1-5). Sons were more willing to get vaccinated if they perceived higher peer acceptance of HPV vaccine (β=0.39) or anticipated higher regret about not getting vaccinated and later developing an HPV infection (β=0.22). HPV vaccine uptake was nearly nonexistent a year after permissive national recommendations were first issued for males. Vaccine acceptability was moderate among both parents and sons. Efforts to increase vaccine uptake among adolescent males should consider the important role of peer acceptance and anticipated regret.