The theory and therapy of Don D. Jackson, MD. is an important piece in the foundation of Marriage and Family Therapy (MFT). It is Jackson's unique Interactional Theory which is viewed by many as the foundation of systemically oriented theories of MFT. This study looked at Jackson's theory and therapy through the eyes of many individuals who worked with him during the most fertile period in MFf history. Individuals such as John Weakland, Murray Bowen, Paul Watzlawick, Jay Haley, Richard Fisch and Jan Beavin-Bavelas were interviewed regarding their understanding of Jackson's influence on the field of MFf. Jackson's theory and therapy were explored in an attempt to gain insight into his unique approach to the therapeutic treatment of individuals within the context of the family. The depth of Jackson's influence on the development of the field is generally recognized however, his influence has been poorly researched. Jackson's departure from the linear orientation of psychoanalysis represents nothing less than a paradigmatic shift. Jackson's Interactional theory was the first theory of human behavior to be grounded in the general systems, communication and cybernetic theories. This change in theoretical orientation laid the foundation for the future development of additional systemically oriented theories and therapies. This dissertation will provide an understanding of Jackson's Interactional theory and therapy as well as provide an understanding of his tremendous influence on the development of systemically oriented family therapies. / Ph. D.