BACKGROUND: The PROUD trial, a HIV prevention trial in men who have sex with men and trans women, set out to involve community representatives and trial participants in several ways. PROUD also aimed to evaluate participant involvement, to learn lessons and make recommendations for future clinical trials. METHODS: Two structured surveys, one of participant and community representatives involved in the PROUD study, and the other of researchers from the PROUD team, were carried out in 2017. The results from the surveys were reviewed quantitatively and qualitatively, and themes emerging from the data identified and synthesised. RESULTS: Survey invitations were sent to 88 involved participants, 11 community representatives and 10 researchers. The overall response rate was 55% (60/109). Overall, participants were younger than community representatives, and the majority were from Greater London. As expected, participants were predominantly involved in participant involvement meetings and community representatives in management committees.Participants and community representatives cited different motivations for getting involved in PROUD. Overall, participants were positive about their involvement; only two participants rated their experience unfavourably. Community representatives were also broadly positive. Most participants and all community representatives felt their involvement made a difference to the trial, themselves and / or the organisations they represented. However, some participant answers reflected the impact of participation in the trial rather than involvement in PPI activities.Researchers felt that PPI had positive impact across the entire trial cycle. Half felt they would have liked there to have been more PPI activity in PROUD. Researchers noted some challenges and recommendations for the future, including need for adequate funding, more engagement in PPI by all researchers, the need for PPI expertise to facilitate involvement activities and training and mentoring in PPI. CONCLUSIONS: Involving clinical trial participants and wider community representatives as active partners in PPI is feasible and valuable in trials. Researchers are encouraged to consider and appropriately resource participant involvement and prospectively evaluate all PPI within their trials.