This paper examines condom use in intimate relationships amongst Papua New Guineans on antiretroviral therapy (ART). These findings are from a mixed-method study in six provinces throughout Papua New Guinea (PNG). A total of 374 HIV-positive adult Papua New Guineans, over the age of 16 and on ART for more than two weeks were recruited using a non-probability, convenience sampling methodology. Participants were recruited through ART prescribing sites, People Living with HIV/AIDS (PLWHA) drop-in clinics and support groups. A small number (36) also participated in in-depth interviews. Of the sample 226 (60.4%) were women and 148 (39.6%) were men. The majority of the sample was aged below 40 years, with a median age of 30 years. Of the sample who were in a regular relationship 64.7% identified themselves as being in a relationship where both they and their partner were HIV-positive (seroconcordant). Smaller proportions (21.0%) reported being in a relationship with a HIV-negative partner (serodiscordant), or in a relationship where they were not aware of their partner's HIV status (14.3%). The majority of participants who reported having a regular partner also reported having disclosed their HIV serostatus to their partner (91.8%). A significantly greater proportion of participants who reported being in relationships where they did not know the status of their partner, also reported living in the Southern Region of PNG (52.9%), while the majority of those in seroconcordant relationships lived in the Highlands Region (71.2%). There did not appear to be any differences in sexual practice of using condoms between the three groups. Knowledge of serostatus is important for "positive prevention".