Fruitfully combining approaches from economic history and the cultural history of commerce, this book examines the role of interpersonal trust in underpinning trade, amid the challenges and uncertainties of the eighteenth-century Atlantic. It focuses on the nature of mercantile activity in two parts of Spain: Cadiz in the south, and its trade with Spain´s American empire; and Bilbao in the north, and its trade with western and northern Europe. In particular, it explores the processes of trade, trading networks and communications, seeking to understand merchant behaviour, especially the choices made by individuals when conducting business - and specifically with whom they chose to deal. Drawing from a broad range of Spanish, Peruvian and British archival sources, the book reveals merchants´ experiences of trusting their agents and correspondents, and shows how different factors, from distance to legal frameworks and ethnicity, affected their ability to rely on their contacts.