In this article, Mary Lacity and Leslie Willcocks review the practice of outsourcing business and information technology services. Research finds that outsourcing can deliver value to client organisations, but that it takes a tremendous amount of detailed management by clients and providers to realise expected benefits. The proven practices that contribute to positive outsourcing outcomes can be summarised as contractual governance, relational governance, client retained capabilities, and provider capabilities. Despite outsourcing's maturity, some enduring contractual challenges remain, particularly in the areas of incentive pricing and contract adaptability.