This chapter discusses the relationships between mission agencies and churches, who are the primary senders of missionaries. It outlines the roles that churches, agencies, trainers, and mobilizers play as shareholders in the mission enterprise. The chapter then addresses some of the challenges in maintaining effective partnerships and carrying out the mission task, including rallying church support, balancing priorities, focusing on unreached people groups, supporting both frontline and support missionaries, and providing long-term missionary care. Effective short-term mission programs and resources for missionary care are also discussed.