The number of men likely or very likely to participate in trials using ARVs to prevent HIV infection (43.2%) was almost double the number willing to participate in rectal microbicide trials, and the number of participants who did not know whether they would participate in trials using ARVs to prevent HIV infection was much lower (7.7%). There were no significant predictors of willingness to participate in trials using ARVs to

prevent HIV infection. Of note, although this result did not reach statistical significance, men who reported UAI in the past 6 months PCI-32765 cost with an HIV-positive partner were nearly twice as likely as men who reported no UAI to respond positively to participating in trials using ARVs to prevent HIV infection (OR 1.82, 95% CI 0.99–3.35; Table 3). Previous awareness of NPEP was not a predictor of willingness to participate in trials using ARVs to prevent HIV infection, either when awareness of NPEP at study enrolment (OR 0.9, 95% CI 0.70–1.37, P=0.90) or awareness of NPEP at the same interview as the last willingness

to participate response (OR 1.99, 95% CI 0.82–4.81, P=0.13) was taken into consideration. The number of participants who had not heard of NPEP was very small (25, 2.8%). Among 1923 person-years of follow-up, no participant reported using PREP. One participant, on one occasion, reported that he was unsure as to whether he had used it. Fewer than 15% of men had heard of rectal microbicides, although around one-quarter (24%) reported that they would consider participation LEE011 solubility dmso in a trial of their use. Older and more highly educated men were more likely Coproporphyrinogen III oxidase to have heard of rectal microbicides. For PREP, a higher proportion of men, approximately 50%, were

willing to participate in trials using ARVs to prevent HIV infection, and willingness was higher among those who reported UAI with HIV-positive partners. There was no evidence of current PREP use within this cohort of HIV-negative gay men. There have been few studies of awareness of microbicides in men. The low level of knowledge of rectal microbicides (13.7%) among HIM participants was consistent with comparable levels of men’s knowledge of such products in other studies. Previous smaller studies in Australian men who reported sex with women [18] and men in New York who reported UAI with men [19] found that the majority of men did not know what microbicides were. In our study, only one-quarter of men were likely or very likely to participate in rectal microbicide trials. Interestingly, among men who had a definite opinion about their likelihood of participation, knowledge of rectal microbicides was inversely related to willingness to participate in rectal microbicide trials. This is perhaps unsurprising given the lack of protective efficacy reported in all published microbicide trials, and the well-publicized rectal toxicity of one putative microbicide, nonoxynol-9 [20].