The relationship in information technology (IT) outsourcing determines the difference between a successful, a less successful, and a failing outsourcing deal. IT managers will commonly spend seventy per cent of their time on making the client-supplier relationship work, while thirty per cent of their time will focus on the contract, personnel, and problem issues. Longitudinal research into Xerox’s global, British Aerospace’s total,ESSO’s selective, British Petroleum’s alliance, and the UK Inland Revenue’s public sector outsourcing deals highlights relationship practices and recurring post-contract management issues that demand careful attention and management. By use of novel cliebt-supplier relationship framework developed from transaction cost, relational contract, nad interorganisational relationship theory, the authors carefully amalyse these five longitudinal case studies and identify what the key dimensions of an outsourcing relationship are. Together the framework and the case studies provide a number for both practitioners and academics on how to achieve a relationship advantage.