This article draws attention to struggles inherent in discourse about the meaning of participation in a Flemish participatory technology assessment (pTA) on nanotechnologies. It explores how, at the project's outset, key actors (e.g., nanotechnologists and pTA researchers) frame elements of the process like 'the public' and draw on interpretive repertoires to fit their perspective. The examples call into question normative commitments to cooperation, consensus building, and common action that conventionally guide pTA approaches. It is argued that pTA itself must reflect an awareness of competing interests and perspectives inherent in the discourse associated with the meaning of 'participation' if it is to incite action beyond vested interests and ensure genuine mutual learning.