This book explores customer-supplier relationships in B2B markets focusing on interaction between parties. Drawing on three fields of research – studies of relationships in marketing, social interactionism in sociology, and sense-making in social psychology – the author explores the concepts and roles of actors in business relationships and how the behaviour of actors within an interaction affects the development of those relationships. Based on a review of prior research and an original empirical study, the author argues that the presence of continuous close relationships between the customer and supplier organisations bestows features of a business network on B2B markets, with distinct interdependencies and ubiquitous interactions. Exploring buyer-seller interactions, the author contends that actors’ mutually perceived identities – continuously emergent and relationship-specific – are the main factor in the development of business relationships and discusses the implications for management practice and research.