This article identifies key characteristics of participatory research and development(R&D) in the agricultural sector: it is client-driven, requires decentralized technology development, devolves to farmers the major responsibility for adaptive testing, and requires institutions and individuals to become accountable for the relevance and quality of technology on offer. Through case study material drawn from Latin America, Asia and Africa, the article then reviews ways by which institutions have responded to these characteristics and raises issues for further elaboration. Steps need to be taken, in particular, to safeguard equity, both between the more and less vocal groups of farmers, and between the requirements of present and future generations (the latter referring particularly to environmental concerns). It is argued that participatory R&D alone is insufficient to deliver innovations relevant to diverse client groups: policy mechanisms are required to define which clients are to participate, whose agendas are to drive the process, and what organizational innovations are needed to move agricultural R&D in these directions.