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. Zequi SC, Guimarães GC, da Fonseca FP, Ferreira U, de Matheus WE, Reis LO, Aita GA, Glina S, Fanni VSS, Perez MDC, Guidoni LRM, Ortiz V, Nogueira L, Rocha LCA, Cuck G, da Costa WH, Moniz RR, Dantas Jr. JH, Soares FA, and Lopes A. Sex with animals (SWA): Behavioral characteristics and possible association with penile cancer. A multicenter study. J Sex Med 2012;9:1877–1884.