Abstract

We report on the relation between various aspects of sexual activity and risk of infection with sexually transmitted disease (STD) in two groups of men attending an STD clinic. Sexual promiscuity appeared to have little effect on the distribution of most STDs, showing a strong association only with gonorrhoea. This finding was contrary to expectation but consistent with the results reported in the first two papers in this series. In contrast to promiscuity, however, sexual orientation subgroups showed a sharp difference in incidence of the major STDs. Hepatitis and syphilis occurred equally commonly among bisexual and homosexual men, but much less commonly among heterosexuals; NSU occurred more commonly among heterosexual men; and gonorrhoea, though common in all three groups, occurred most commonly in bisexual men and least commonly among heterosexuals. For certain STDs the form of intercourse may be as important a risk factor as sexual promiscuity but the precise mechanisms by which sexual orientation influences risk of STD remain undefined.