The doctrine of union with Christ lies at the center of God's redemptive relationship to fallen human beings. It is foundational to all that God has redemptively done for us in the past, is doing for us in the present, and will do for us in the future. It is the key to understanding the whole of what is meant by salvation. The purpose of this book is to make some contribution towards reasserting the primary import of this foundational doctrine. Four basic questions are dealt with: (1)Who is united with Christ? What is the basis of this union? (2)When is one united with Christ? What is the time of this union? (3)How is one united with Christ? What is the nature of this union? (4)What are the benefits of union with Christ? What is the fruit of this union? In exploring the answers to these questions, the reader will discover the New Testament teaches that Christ is personally united with elect believers (at that moment in history when they make a decision of faith) in a unique, dynamic and permanent spiritual union that results in union with the triune God and other believers, divorce from the world of unbelief and reception of the blessings of the Kingdom of God.