This article investigates how banks build competitive advantage through relationship banking. Using a grounded theory approach, 29 interviews were conducted with relationship managers and corporate banking directors in 21 case banks from 2004 to 2008. Grounded theory models were developed to illustrate the value creation process in relationship banking. It was found that long-term bank-corporate relationships were established through trust-based personal communications. In the case, banks customer information and knowledge advantages were created. Risk-adjusted returns on assets were used to measure customer relationship performance, and relationship managers were rewarded accordingly. The interviewees thought that bank performance could be improved by managing customer credit risk and identifying cross-selling opportunities. This study starts to open up the 'black box' of how banks create shareholder value through relationship banking, provides a picture of relationship banking as a social phenomenon, and supplies some theoretical and managerial implications. The article also links the literature relevant to relationship banking from different disciplines. This is a new way of looking at the relationship banking phenomenon and relevant literature in an integrated manner.