When historians today assess the behaviour of actors, they generally privilege their limited rationality or their emotions. Another dimension needs however to be emphasized: their actions and reactions in situations of uncertainty. The focus here is on technological uncertainty, as it appears in the design and production of goods or even in their uses by businesses, public organizations (whether civilian or military) or by consumers. It is a very common experience, which is not limited to contemporary history, far from it. It may lead to catastrophes and bring about far-ranging changes of organization, production or of scientific knowledge. Recent researches achieved by historians in the USA throw a new light on the deliberate opacity of certain technological devices and its political dimensions, on the distinction between cognitive, material and prospective technological uncertainty and on the practices developed by industry and by craftsmen: from local sociability to the sharing of intellectual resources available nationally, to cooperation with universities and to the creation of probabilistic devices. They call social sciences to rethink the economy as shaped by processes of exploration embedded in legal regimes and to reconsider the relationship of women and men to artefacts along time and space.