This monograph brings the reader up to date on the basic therapeutic mechanism of glucocorticoid action in the treatment of various lymphoproliferative diseases, most notably in acute lymphoblastic leukemias. As a target protein, the structure and function of both the intracellular and plasma membrane-associated glucocorticoid receptors are reviewed. The various functional domains of the glucocorticoid receptor interaction with a variety of heat shock proteins, transcription factors and specific DNA sequences and how this leads to biological response are addressed. The book aims at leading not only to a better understanding of how glucocorticoid hormones impart their therapeutic effect, but also to the eventual development of efficient diagnostic tools for the identification of hormone-responsive leukemic patients.