Retention is considered to be one of the most fascinating and most important aspect of orthodontic treatment as far as treatment results and stability from the patient is concerned from the operator's point of view. Long back it had been called as the stepchild of orthodontics since no attention was paid towards this aspect. Even today debate still continues regarding post treatment stability and the role-played by retainers in providing this stability. Even after so much of advancement, great deal of studies; research is still required on this subject.Our results will improve as we strive for perfection and realistically balance the scale with more planning for retention. A thorough knowledge of retention is necessary for those of us who bruised egos and a desire to improve. Our Orthodontic forefathers has faced the problems of retention and the continued trend, which owes to the biological and mechanical limitations, demands every Orthodontic student to go through the state of art of this perineal problem "Retention and Relapse" which also is the purpose of this textbook.