Background: The prevention of intimate partner transmission of HIV remains an important component of comprehensive HIV prevention strategies. In this paper we examine the sexual practices of people living with HIV on antiretroviral therapy (ART) in Papua New Guinea (PNG). Method: In 2008, a total of 374 HIV-positive people over the age of 16 and on ART for more than two weeks were recruited using a non-probability, convenience sampling methodology. This accounted for around 18% of adults on ART at the time. A further 36 people participated in semi-structured interviews. All interviews were thematically analysed using NVivo qualitative data analysis software.Results: Less than forty per cent (38%) of participants reported having had sexual intercourse in the six months prior to the survey. Marital status was by far the most important factor in determining sexual activity, but consistent condom use during vaginal intercourse with a regular partner was low. Only 46% reported consistent condom use during vaginal intercourse with a regular partner in the last six months, despite 77% of all participants reporting that consistent condom use can prevent HIV transmission. Consistent condom use was lowest amongst married couples and those in seroconcordant relationships. The vast majority (91.8%) of all participants with a regular heterosexual partner had disclosed their status to their partner. Qualitative data reinforced low rates of sexual activity and provided important insights into sexual abstinence and condom use.Conclusions: Considering the importance of intimate partner transmission of HIV, these results on the sexual practices of people with HIV on ART in PNG suggest that one-dimensional HIV prevention messages focussing solely on condom use fail to account for the current practices and needs of HIV-positive people, especially those who are married and know their partners' HIV status.