1.  MSM, specifically HIV-positive MSM, have a high risk of anal cancer caused by human papillomavirus (HPV).  It has been suggested that MSM attending STI clinics should be offered HPV vaccination.  It is unknown whether clients of STI clinics would like to be vaccinated against HPV. Background  Study population: MSM aged ≥18 years who visit the STI clinic in Amsterdam.  Web-based survey, designed to be completed on a mobile phone during the waiting time at the STI clinic.  Socio-psychological factors derived from the Theory of Planned Behavior and Social Cognitive Theory.  Univariable and multivariable logistic regression analyses.  Intention to get vaccinated was dichotomized as: positive intention versus any doubt up to negative intention to get vaccinated against HPV.  To assess determinants of HPV vaccination acceptability among HIV-negative and HIV-positive MSM.  To assess differences in HPV vaccination acceptability between HIV-negative and HIV-positive MSM. Methods Objectives Figure 1: Intention to get vaccinated against HPV within Three age groups stratified by HIV status  MSM have a high intention to get vaccinated against HPV.  In univariable analysis HPV vaccination intention is significantly higher in HIV-positive MSM compared to HIV- negative MSM.  In multivariable analysis HIV-status was not a significant predictor of vaccination intention.  Attitude towards vaccination, anticipated regret when not vaccinating against HPV and risk perception are important predictors of intention to get vaccinated against HPV.  These factors may be important targets for health promotion strategies that aim to increase HPV vaccination acceptability among MSM. E. Marra 1, C.J. Alberts 1,4, G.D. Zimet 2, T.G.W.M. Paulussen 3, T. Heijman 1, A.A. Hogewoning 1,4, G.J. Sonder 1, J.S. Fennema 1, H.J.C. de Vries 1,4, M.F. Schim van der Loeff 1,4 1. Department of Infectious Diseases, Public Health Service Amsterdam, Amsterdam, The Netherlands 2. Section of Adolescent Medicine, Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana, United States of America 3. Expertise Center Life Style, Netherlands Organization for Applied Scientific Research (TNO), Leiden, The Netherlands 4. Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands. emarra@ggd.amsterdam.nl  Not all variance in the intention to get vaccinated against HPV was explained. This might be due to (1) the necessary limitation in the number of questions asked per socio-psychological factor that could be included in the questionnaire, and (2) socio-psychological factors influencing HPV vaccination intention (direct or indirect) might be missed due to limitation in the number of questions included in the questionnaire.  This analysis implies that HPV vaccination intention is mainly attitudinal driven behavior. Discussion  HIV-positive MSM were significantly older, reported a higher number of anal sexual partners in the preceding 6 months and had more lifetime sexual partners (all P<0.001).  HIV-positive MSM had a higher intention to get vaccinated against HPV than HIV-negative MSM [81% vs. 55%; crude odds ratio (cOR) 2.5; 95% CI: 1.5-4.4; adjusted odds ratio (aOR) 1.7; 95% CI: 0.8-3.9]  Factors significantly associated with intention to get vaccinated against HPV in multivariable logistic regression (R 2 0.45):  Risk perception of HPV related diseases (OR 1.3; 95% CI: 1.0-1.6 )  Anticipated regret when not vaccinating against HPV (OR 1.4; 95% CI: 1.0-1.8)  Attitude towards vaccination (OR 7.7; 95% CI: 5.1-11.5 ) Intention to get vaccinated against human papillomavirus among HIV- negative and HIV-positive MSM Conclusions Results Table 1. Socio-psychological factors influencing intention to get vaccinated against HPV, the differences between HIV-negative and HIV-positive MSM measured on a Likert Scale ranging from -3 to 3 TotalHIV-negativeHIV-positive (n = 438)(n = 343)(n = 95)P value Mean (SD) Intention to get vaccinated against HPV 2.2 (1.2) 2.6 (0.8)<0.001 Attitude towards vaccination2.2 (1.1)2.1 (1.0)2.4 (1.0)0.002 Risk perception of acquiring HPV related diseases 0.1 (1.4) -0.8 (1.3)0.9 (1.2)<0.001 Anticipated regret of HPV infection2.3 (0.9)2.0 (1.0)2.5 (0.8)<0.001 Anticipated regret of not vaccinating2.3 (1.1)2.2 (1.1)2.3 (1.0)0.173 Beliefs regarding HPV vaccination1.6 (1.4) 1.7 (1.6)0.241 Outcome expectancy2.3 (1.7)2.3 (1.6)2.5 (1.7)0.123 Injunctive norm*6.8 (7.3)6.9 (7.0)7.7 (7.6)0.430 * Injunctive norm measured on a Likert Scale from -21 to 21 P=0.179 P=0.092 P<0.001