Although attention has focused on whether participants actually derive better medical outcomes in research, the social benefits experienced in research have not been systematically examined. At regular follow-up visits during a phase III randomized trial assessing the safety and efficacy of a long-term versus a short-term drug treatment intervention in decreasing HIV transmission and mortality conducted in China and Thailand, participants identified research-related negative and positive social impacts (PSIs). Open-ended PSI responses were coded using standard qualitative techniques. Among 1025 participants, only 4 reported a negative social impact; however, 77% reported at least one PSI over the 104 week follow-up period. Given the high prevalence of PSIs we observed, future research should embed assessments of negative and positive social impacts experienced by participants in research not only to ensure their well-being, but also to inform policy and conceptual work related to research ethics.