1 So what difference does it make? - assessing the outcomes and impacts of farmer participatory research. Adrienne Martin Abstract This paper provides a brief overview of what constitutes valid evidence for the efficacy and impact of participatory research drawing on the participatory research impact assessment literature and the author‟s experience of advising, reviewing and evaluating projects and programmes which have participatory research components, or are undertaking research within multistakeholder participatory processes. There has been important progress in demonstrating the different outcomes made by participatory approaches, but there remain differences in how the contribution of participatory research is judged, what evidence is considered valid and by whom. Introduction Early work in participatory research was concerned with both with a value orientation in research – values of participation and empowerment, and a pragmatic emphasis on achieving greater relevance of research, particularly for resource poor farmers through conducting agricultural research with the active participation of potential users of research outputs. The literature of the 1980s focused on the many examples of approaches and tools which facilitated this participation, primarily in the technology development process. Evidence was primarily drawn from case studies, identifying common issues and synthesising lessons. Unsurprisingly, it was noted in the early years of participatory research, that “the effectiveness of participatory methods in terms of time and costs is rarely assessed” and that “several case studies of projects using innovative methods at the outset … have not yet produced an evaluation of their experience”. (Farrington and Martin, 1988:30). Subsequent work broadened to include the institutional and policy context for participatory research, focusing on institutional change, policy dimensions and stakeholder relationships. However, it seems that despite the great wealth of participatory experience, and a large body of literature on the impact of research and development programmes, including impact of participatory research (under the PRGA 1 amongst others), that there is still a significant degree of controversy on how the impact of participatory research approaches should be assessed. This is becoming more relevant as agricultural research is increasingly located within multistakeholder innovation platforms and integrated research for development processes. This paper is a short reflection on what constitutes valid evidence for the efficacy and impact of participatory research drawing in part on the large impact assessment literature and my own experience of advising, reviewing and evaluating projects and programmes which have participatory research components, or are undertaking research within multistakeholder participatory processes. It suggests that there has been important progress in demonstrating the difference in outcomes and impacts made by participatory approaches, but there remain differences in how the contribution of participatory research is judged, what evidence is considered valid and by whom. What difference? – the construction of comparisons. Judging impact or assessing the difference made by FPR involves some form of comparison. There are different models of comparison, for example, „before and after‟ comparisons‟, assessing change against planned outputs and outcomes using specified indicators; methods which track change over time, such as outcome mapping (Earl et el, 2001) and Most 1 Participatory Research and Gender Analysis – CGIAR System Wide Initiative.