Objectives: This study was designed to evaluate the immunogenicity and tolerability of a prophylactic 9-valent HPV (types 6/11/16/18/31/33/45/52/58) VLP (9vHPV) vaccine in young men 16-26 years of age in comparison to young women 16-26 years of age (the population that was used to establish 9vHPV vaccine efficacy). Safety and immunogenicity data from this study will be used to bridge 9vHPV vaccine efficacy findings in 16-26 year old women to 16-26 year old men. Methods: This study enrolled 1106 heterosexual men (HM) and 1101 women who had not yet received HPV vaccination. In addition, 313 men having sex with men (MSM) were enrolled and were evaluated separately for immunogenicity because previous results showed that antibody responses to quadrivalent HPV (types 6/11/16/18) VLP (qHPV) vaccine were lower in MSM than in HM. All subjects were administered a 3-dose regimen (Day 1, Month 2, Month 6) of 9vHPV vaccine. Serum samples were collected for anti-HPV assays. Safety information was collected for ~12 months. Results: The geometric mean titers (GMTs) for HPV types 6, 11, 16, 18, 31, 33, 45, 52, and 58 for HM were non-inferior to those of women at Month 7. For all vaccine HPV types, Month 7 GMTs were numerically lower in MSM than in HM. Over 99.5% of subjects were seropositive at Month 7 for each vaccine HPV type. Administration of 9vHPV vaccine to both 16-26 year old men and women was generally well tolerated. Conclusions: These results support bridging the efficacy findings with 9vHPV vaccine in young women 16-26 years of age to men 16-26 years of age.