Introduction. Zoophilia has been known for a long time but, underreported in the medical literature, is likely a risk factor for human urological diseases. Aim. To investigate the behavioral characteristics of sex with animals (SWA) and its associations with penile cancer (PC) in a case-control study. Methods. A questionnaire about personal and sexual habits was completed in interviews of 118 PC patients and 374 controls (healthy men) recruited between 2009 and 2010 from 16 urology and oncology centers. Main Outcome Measures. SWA rates, geographic distribution, duration, frequency, animals involved, and behavioral habits were investigated and used to estimate the odds of SWA as a PC risk factor. Results. SWA was reported by 171 (34.8%) subjects, 44.9% of PC patients and 31.6% of controls (P<0.008). The mean ages at first and last SWA episode were 13.5 years (standard deviation [SD] 4.4 years) and 17.1 years (SD 5.3 years), respectively. Subjects who reported SWA also reported more venereal diseases (P<0.001) and sex with prostitutes (P<0.001), and were more likely to have had more than 10 lifetime sexual partners (P<0.001) than those who did not report SWA. SWA with a group of men was reported by 29.8% of subjects and SWA alone was reported by 70.2%. Several animals were used by 62% of subjects, and 38% always used the same animal. The frequency of SWA included single (14%), weekly or more (39.5%), and monthly episodes (15%). Univariate analysis identified phimosis, penile premalignancies, smoking, nonwhite race, sex with prostitutes, and SWA as PC risk factors. Phimosis, premalignant lesions, smoking, and SWA remained as risk factors in multivariate analysis. However, SWA did not impact the clinicopathological outcomes of PC. Conclusion. SWA is a risk factor for PC and may be associated with venereal diseases. New studies are required in other populations to test other possible nosological links with SWA. © 2011 International Society for Sexual Medicine.9718601867Curado, M.P., Edwards, B., Shin, H.R., Storm, H., Ferlay, J., Heanue, M., Boyle, P., (2007) Cancer incidence in five continents, 9. , [IARC Scientific Publications, 160]. Lyon: IARCPow-Sang, M.R., Ferreira, U., Pow-Sang, J.M., Nardi, A.C., Destefano, V., Epidemiology and natural history of penile cancer (2010) Urology, 76 (1), pp. S2-S6. , SUPPLMiralles-Guri, C., Bruni, L., Cubilla, A.L., Castellsagué, X., Bosch, F.X., de Sanjosé, S., Human papillomavirus prevalence and type distribution in penile carcinoma (2009) J Clin Pathol, 62, pp. 870-878Maden, C., Sherman, K.J., Beckmann, A.M., Hislop, T.G., Teh, C.Z., Ashley, R.L., Daling, J.R., History of circumcision, medical conditions, and sexual activity and risk of penile cancer (1993) J Natl Cancer Inst, 85, pp. 19-24Sobin, L.H., Wittekind, C., (2002) TNM classification of malignant tumors, , eds. 6th edition. New York, NY: Wiley & SonsWilliams, C.J., Weinberg, M.S., Zoophilia in men: A study of sexual interest in animals (2003) Arch Sex Behav, 32, pp. 523-535Miletski, H., (2002) Understanding bestiality and zoophilia, p. 273. , Bethesda, MD: East-West Publishing LLCShenken, L.I., Some clinical and psychopathological aspects of bestiality (1964) J Nerv Ment Dis, 139, pp. 137-142Karpman, B., (1954) The sexual offender and his offenses: Etiology, pathology, psychodynamics, and treatment, , New York: Julian PressKinsey, A.C., Pomeroy, W.B., Martin, C.E., (1948) Sexual behavior in the human male, , Philadelphia: W.B. SaundersAlvarez, W.A., Freinhar, J.P., A prevalence study of bestiality (zoophilia) in psychiatric in-patients, medical in-patients and psychiatric staff (1991) Int J Psychosom, 38, pp. 45-47Tseng, H.F., Morgenstern, H., Mack, T., Peters, R.K., Risk factors for penile cancer: Results of a population-based case-control study in Los Angeles County (United States) (2001) Cancer Causes Control, 12, pp. 267-277Daling, J.R., Madeleine, M.M., Johnson, L.G., Schwartz, S.M., Shera, K.A., Wurscher, M.A., Carter, J.J., Krieger, J.N., Penile cancer: Importance of circumcision, human papillomavirus and smoking in in situ and invasive disease (2005) Int J Cancer, 116, pp. 606-616Hellberg, D., Valentin, J., Eklund, T., Nilsson, S., Penile cancer: Is there an epidemiological role for smoking and sexual behaviour? (1987) Br Med J (Clin Res Ed), 295, pp. 1306-1308Wideroff, L., Schottenfield, D., Penile cancer (2006) Cancer epidemiology and prevention, pp. 1166-1172. , Schottenfeld D, Fraumeni JF, eds. New York: Oxford University PressEdlin, R.S., Aaronson, D.S., Wu, A.K., Blaschko, S.D., Yang, G., Erickson, B.A., McAninch, J.W., Squamous cell carcinoma at the site of a Prince Albert's piercing (2010) J Sex Med, 7, pp. 2280-2283Favorito, L.A., Nardi, A.C., Ronalsa, M., Zequi, S.C., Sampaio, F.J., Glina, S., Epidemiologic study on penile cancer in Brazil (2008) Int Braz J Urol, 34, pp. 587-591Crispen, P.L., Mydlo, J.H., Penile intraepithelial neoplasia and other premalignant lesions of the penis (2010) Urol Clin North Am, 37, pp. 335-342Velázquez, E., Peix, A., Gómez-Alonso, A., Microorganisms and cancer: Scientific evidence and new hypotheses (2011) Cir Esp, 89, pp. 136-144Dalton-Griffin, L., Kellam, P., Infectious causes of cancer and their detection (2009) J Biol, 8, p. 67Urisman, A., Molinaro, R.J., Fischer, N., Plummer, S.J., Casey, G., Klein, E.A., Malathi, K., DeRisi, J.L., Identification of a novel Gammaretrovirus in prostate tumors of patients homozygous for R462Q RNASEL variant (2006) PLoS Pathog, 2, pp. e25Silverman, R.H., Nguyen, C., Weight, C.J., Klein, E.A., The human retrovirus XMRV in prostate cancer and chronic fatigue syndrome (2010) Nat Rev Urol, 7, pp. 392-402Mehrpour, M., Codogno, P., Prion protein: From physiology to cancer biology (2010) Cancer Lett, 290, pp. 1-23Gärtner, H.V., Seidl, C., Luckenbach, C., Schumm, G., Seifried, E., Ritter, H., Bültmann, B., Genetic analysis of a sarcoma accidentally transplanted from a patient to a surgeon (1996) N Engl J Med, 335, pp. 1494-1496Dingli, D., Nowak, M.A., Cancer biology: Infectious tumour cells (2006) Nature, 443, pp. 35-36Murgia, C., Pritchard, J.K., Kim, S.Y., Fassati, A., Weiss, R.A., Clonal origin and evolution of a transmissible cancer (2006) Cell, 126, pp. 477-487Rebbeck, C.A., Thomas, R., Breen, M., Leroi, A.M., Burt, A., Origins and evolution of a transmissible cancer (2009) Evolution, 63, pp. 2340-2349van den Top, J.G., de Heer, N., Klein, W.R., Ensink, J.M., Penile and preputial tumours in the horse: A retrospective study of 114 affected horses (2008) Equine Vet J, 40, pp. 528-532Gao, F., Bailes, E., Robertson, D.L., Chen, Y., Rodenburg, C.M., Michael, S.F., Cummins, L.B., Hahn, B.H., Origin of HIV-1 in the chimpanzee Pan troglodytes troglodytes (1999) Nature, 397, pp. 436-441Weiss, H.A., Thomas, S.L., Munabi, S.K., Hayes, R.J., Male circumcision and risk of syphilis, chancroid, and genital herpes: A systematic review and meta-analysis (2006) Sex Transm Infect, 82, pp. 101-109Gray, R.H., Kigozi, G., Serwadda, D., Makumbi, F., Watya, S., Nalugoda, F., Kiwanuka, N., Wawer, M.J., Male circumcision for HIV prevention in men in Rakai, Uganda: A randomised trial (2007) Lancet, 369, pp. 657-666Tobian, A.A., Serwadda, D., Quinn, T.C., Kigozi, G., Gravitt, P.E., Laeyendecker, O., Charvat, B., Gray, R.H., Male circumcision for the prevention of HSV-2 and HPV infections and syphilis (2009) N Engl J Med, 360, pp. 1298-1309