The curator Lionello Puppi was engaged for years both in the document retrieval in several European countries, but also in the reorganization of Titian's archive preserved by the Magnificent Community of Cadore. It was collected valuable material for the purposes of a detailed knowledge of the biographical events of Master Cadorino, but also about ways of carrying out its activities, both artistic and entrepreneurial, material now scattered in various locations, both public and private. This publication presents the complete edition of letters sent and received by Titian in his lifetime, and more precisely since 1513 to 1576. The edition is characterized by detailed comments which, in light of recent studies of Titian, clarify and illuminate circumstances promptly, previously escaped the attention of specialists, about the troubled and difficult relationships between the Master and his clients (the Farnese Circle, Philip II of Spain's Court), but even with close friends, starting with Pietro Aretino.