Necessity of research of teenagers after violent actions of sexual character is connected basically with anogenital sexual contacts. Survey of victims by the medicolegal (forensics medicines) expert assumes knowledge of illnesses like anorectal complex, causing anorectal dysfunctions (perianal itch, proctalgia, a crack of anal tract, encopresis). All specified diseases concerned with anorectal rings can be idiopatic (without the established reason) and secondary (locks, violent actions of sexual character, medical manipulations, traumas). On suspicion of anal penetration in children, survey should be carried out after obligatory conversation with the psychologist and with special feeling of a step, taking into account age factors and diseases of mental sphere. Such survey demands a certain algorithm of inspection, whose basic stages consist of the following: (1) Survey of anal areas will be carried out after preliminary conversation and examinations of other sites of a body in knee-elbow position. Whenever possible, the expert should be on floor with surveyed. (2) Hands of the expert should be warm so as not to provoke a pressure of muscles in the anus. (3) The anal reflex is checked by an easy touch, without painful variant, to a superficial part anal apertures (external sphincter is tunicae reduced, back pass is involved). (4) Children, as a rule, do not keep sphincter, a strong-willed pressure and therefore, reduction of a reflex is accompanied by reduction of force as a result of reduction of sphincter and its tone.