Male homosexual behaviour is not simply either "active" or "passive", since penile-anal, mouth-penile, and hand-anal sexual contact is usual for both partners, and mouth-anal contact is not infrequent. A simplified method for recording sexual behaviour--a "sexual behaviour record (SBR)"--can be of value in determining the sites to be investigated and as a basis for further epidemiological questioning. Mouth-anal contact is the reason for the relatively high incidence of diseases caused by bowel pathogens in male homosexuals. Trauma may encourage the entry of micro-organisms and thus lead to primary syphilitic lesions occurring in the anogenital area. Similarly, granuloma inguinale, condylomata acuminata, and amoebiasis may be spread from the bowel of the passive homosexual contact. In addition to sodomy, trauma may be caused by foreign bodies, including stimulators of various kinds, penile adornments, and prostheses.