This article presents the integration of traditional data collection methods for the evaluation of an HIV-prevention programme for Vietnamese sex workers in Cambodia with a participatory approach to project implementation. Local instability and powerlessness posed serious challenges to maintaining our commitment to the principles of participation and ensuring rigorous research. The project consequently focused on negotiating these challenges and adapting the study. Although our efforts did not fully harness the empowering potential of participation and raised a series of contradictions in our design, we gained a rich understanding of the complex community dynamics in this marginalized population. Our experience highlights the need for careful consideration of what participation can feasibly hope to achieve in severely constrained settings, but suggests it can contribute to critical knowledge for the development of appropriate interventions.