H.P. BLAVATSKY (1831-1891) completed The Key to Theosophy in 1889, less than a year after publication of her monumental work The Secret Doctrine. As she says in her Preface, "It traces the broad outlines of the Wisdom Religion, and explains its fundamental principles, while meeting, at the same time, the various objections raised by the average Western enquirer." H.P.B. (as she was known to her students) endeavors to "present unfamiliar concepts in a form as simple and in language as clear as possible." The Key is written as a dialogue between a Theosophist and a somewhat skeptical inquirer, and over the years students have found it an invaluable textbook. In its fifteen chapters, Blavatsky points out the historical roots of Theosophy and sets forth a concise and approachable presentation of its main teachings. These include the concept of Deity as an impersonal, universal and unifying principle; the ideas of Karma and reincarnation as dynamics of human growth and evolution; and the various animating principles, both physical and transcendental, which make up the human being. While many of these ideas may not seem as unfamiliar as they did in 1889, having since been absorbed into the vocabulary of contemporary life, their meanings are often neither fully nor practically understood. Perhaps most importantly, H.P.B. places a great emphasis throughout on the profound moral implications of these age-old teachings. That these transforming aspects of the ancient Wisdom Religion might be made more widely known and find expression in the minds, hearts, and daily lives of those who take up this study was the mission of her life's work. The present publication is a verbatim reproduction of the original edition of 1889 and carefully preserves its layout and pagination. To this has been added both the Preface H.P.B. wrote to the second edition of 1891 and the Glossary of terms included with that edition.