In the last twenty years or so, sociologists have shown that trust is an especially problematic but also especially important feature of modern societies, in which traditional and familiar social ties have been broken up and reconfigured in new patterns. On the whole, however, sociologists do not attempt a historical analysis, contenting themselves with the distinction between modern and pre-modern societies. With few exceptions, historians, who could give a more differentiated account, have not shown much interest in trust. Even those who deal with themes like religion, ethnicity, gender and the family tend to interpret them through power relationships rather than trust relationships. There are very good reasons, though, why historians should tackle the theme of trust. In this essay it is argued that the manner in which trust works in any given society is vital to the understanding of most social phenomena. An account is attempted of certain crucial junctures in European history when the radius of trust has broadened relatively rapidly. Finally the essay offers some suggestions as to why a perceived ‘crisis of trust’ has arisen, both in the contemporary western world and in the global economy, and what might be done about it.