The prevalence of bestiality (both actual sexual contacts and sexual fantasy) was investigated in an experimental group (psychiatric in-patients) and two control populations (medical in-patients and psychiatric staff). Psychiatric patients were found to have a statistically significant higher prevalence rate (55%) of bestiality than the control groups (10% and 15% respectively). Implications of these findings are discussed. It is recommended that due to the obvious prevalence of this condition, questions exploring this previously ignored topic should be routinely included in the psychiatric interview.