Agile methods such as XP emphasize the adaptation to changes, the collaboration with customers and the role of individuals. The project manager, developer and customer should have a tactic to handle the uncertain factors and the management conflicts in software development process. XP ′ s on-site customer practice makes the customer play a important role in development process, and facilitate the broad collaboration between developer and customer. Based on the feature of XP project life cycle and practices, this paper explores respective activities and responsibilities between development team and customer team, and the issues in their collaboration. Some practices in which customer participates is addressed, the activities of both developer and customer are described, some probable problems when customer and programmer work together are presented, and a formal example is given. © 2008 IEEE.