Transsexualism and transvestism are classified as gender disorders; fetishism is a displacement disorder. The outward signs of gender disorientation that characterize transsexualism are described and distinguished from homosexuality and transvestism. The implications of the 2-year real-life test, during which the preoperative transsexual must live totally in the role of the opposite sex before undergoing irreversible sex reassignment surgery, are discussed. Police are advised to be aware of the probable absence of criminal intent of preoperative transsexuals, who are urged to carry letters identifying their condition. Transvestism is defined as cross-dressing for the sake of sexual arousal and to release anxiety about gender role identity. Passing in 'straight' society dressed as a woman is described as the ultimate pleasure of the transvestite who, however, encounters serious personal problems related to his unusual needs, for which there is no known cure. Therapy is often prescribed as a means of keeping the disorder within acceptable social limits. Police are advised to question transvestites to identify criminals who dress as women for purpose of disguise in order to commit crimes. Fetishism is a disorder in which a particular object is the sole source of erotic arousal. It is a sexual disorder that may originate as far back as childhood. Described as a biological or psychological disorder, compulsive fetishistic behavior is viewed as necessary to work off mounting sexual tension. Police are urged to realize that transsexual, transvestite and fetishist behavior is often not voluntary, nor is it subject to prosecution in most jurisdictions. However, persons known to be suffering from such disorders should be occasionally questioned in cases were a criminal uses cross-dressing as a disguise for committing crimes. A discussion guide covering voyeurism, obscene phone calls, and indecent exposure is included.