Current discussions on public trust, as well as on risk communication, have a restricted rationalistic bias in which the cognitive-reflexive aspect of trust is emphasized at the expense of its emotional aspect. This article contributes to a substantive theory of trust by exploring its emotional character. Drawing on recent discussions in science and technology studies, social psychology, and general social theory, it argues that trust is a modality of action that is relational, emotional, asymmetrical, and anticipatory. Hence, trust does not develop through information and the uptake of knowledge but through emotional involvement and sense-making. The implications of this conception of trust for public understandings of science and for risk communication are discussed.