). Data were collected between November 2005 and February 2009. Assessments were administered using audio-computer-assisted structured interviews (ACASIs). Participants viewed assessment items on a 15-in. colour monitor, heard items read by machine voice using headphones, and responded by clicking a mouse. Research has shown that ACASI procedures yield reliable responses in sexual behaviour interviews, with higher BYL719 in vitro response rates than obtained from face-to-face interviews [23]. Participants were instructed in how to use the mouse prior to the assessment. Although 37% of participants had not used a computer

in the previous 2 months, few difficulties were encountered by participants completing the assessments. Participants were asked their age, years of education, income, ethnicity and employment status. We assessed HIV-related symptoms using a previously developed and validated measure of 14 common symptoms of HIV disease. Participants indicated whether they had ever been diagnosed with an AIDS-defining condition and their most recent CD4 cell count and viral load. Participants reported whether they had been diagnosed with a non-HIV STI during a 6-month window. Data were collected at the initial assessment for the previous 3 months and again 3 months later. Participants who indicated that they had been diagnosed with an STI in either

of the 3-month time blocks were

high throughput screening assay defined as having a recent STI diagnosis. We asked which STIs participants were diagnosed with, and the STI symptoms they experienced. Participants responded to questions assessing their number of male and female sexual partners new and frequency of sexual behaviours in the previous 3 months. Specifically, vaginal and anal intercourse with and without condoms was assessed within seroconcordant (i.e. same HIV status) and serodiscordant (i.e. HIV-positive and HIV-negative mixed) partnerships. A 3-month retrospective period was selected because previous research has shown reliable reports for numbers of partners and sexual events over this time period [24]. Participants were instructed to think back over the past 3 months and estimate the number of sexual partners they had had and the number of occasions on which they practised each sexual behaviour. The instructions included cues for recollecting behavioural events over the past 3 months. Our measure of infectiousness beliefs was adapted from previous research [25] and included four items: ‘People with HIV who take HIV medications are less likely to infect their sex partners during unsafe sex’; ‘HIV treatments make it easier to relax about unsafe sex’; ‘It is safe to have sex without a condom when my viral load is undetectable’; and ‘People with an undetectable viral load do not need to worry so much about infecting others with HIV’.