Recent science and technology studies have analyzed questions of nonexpert participation in science, technology, and science policy from an empirically grounded perspective. The introduction to this special issue offers a double contribution to this debate. First, it presents a summary of the state of the art and an outline of the historical emergence of the participatory question. The argument distinguishes four periods since the late nineteenth century, each with a specific relationship between expert and nonexpert knowledge ranging from a hybrid, (...) to a politicized, to an autonomous, to a participatory relationship. Second, the introduction summarizes the contributions to this issue. Their common concern is to take the debate one step further by critically reflecting the problems and limitations of participatory practices. The contributions point out the need for contextualizing the participatory question within the wider social, economic, and political circumstances in which participatory science and technology is set. (shrink)