Background Concurrent relationships are a driver of generalised epidemics of sexually transmissible infections (STIs). In Australia, explicit negotiation of agreements about sex outside regular relationships has been recommended in health promotion for gay @entity1 but not for heterosexuals. OBJECTIVE: To ascertain the annual incidence of concurrency among @entity1 in ongoing male-female relationships according to their reported expectations of exclusivity. METHODS: In a national cohort recruited by household random digit dialling in 2004-05, @entity1 aged 16-64 years completed computer-assisted telephone interviews including questions about expectations of @entity458 , discussion and agreements. A year later, those in ongoing sexual relationships (5323 @entity1 ) were asked about sexual partner numbers in the past year. RESULTS: The huge majority (96%) expected @entity458 of themselves and their partner. However, only 48% of @entity1 and 64% of @entity1 had discussed the matter and explicitly agreed. Older respondents were less likely to report discussion. Only 1% reported mutually nonexclusive ('open') relationships. A year later, 93% of respondents were still in the same relationship, among whom 4% of @entity1 and 2% of @entity1 had had sex outside the relationship. Those with agreements that one or both partners could have sex with others were more likely to do so, but the majority of respondents who had sex with someone else were in relationships that were explicitly or implicitly expected to be exclusive. CONCLUSIONS: Sexual health promotion should stress the importance of STI testing and establishing agreements about exclusivity before condoms are abandoned in new relationships.

Who's cheating? Agreements about XXXX and subsequent concurrent partnering in Australian heterosexual couples.

@entity1 :: ('9606', 'Species') :: ['people', 'women', 'men'] @entity458 :: ('MESH:D020018', 'Disease') :: ['sexual exclusivity']
@entity458 :: (MESH:D020018,Disease) :: ['sexual exclusivity']
