How are the conflicts over the use of certain technologies - such as biotechnology, nuclear energy or nanotechnologies - being solved? What are the methods used by conflicting parties to assert their definitions of reality? What role do uncertainties and risks play in these conflicts? How are they treated? What strategies are used by proponents and opponents of a controversial technology to persuade the public and decision-makers? This article aims at finding answers to these questions by looking at technological conflicts from the perspective of the reduction of risks and uncertainty. The lesson drawn from the study of ongoing and past conflicts over controversies in technological development should help to better understand the dynamics of conflicts focused on converging technologies. The reduction of uncertainty is analyzed from the perspective of the sociology of non-knowledge and ignorance. It is argued that new areas of non-knowledge are being created by reducing uncertainty and risks in technological conflicts. © 2009 Interdisciplinary Centre for Comparative Research in the Social Sciences and ICCR Foundation.