Riso, Don Richard and Russ Hudson, Discovering Your Personality Type, 3rd ed., Boston: Houghton-Mifflin Co., 2003. A basic but excellent general introduction to the Enneagram types, highly accessible to beginners. Includes an extensive self-test, the scientifically validated RHETI, v. 2.5.

Riso, Don Richard and Russ Hudson, Understanding the Enneagram, rev. ed., Boston: Houghton-Mifflin Co., 2000. An authoritative guide to the Enneagram with emphasis on its practical application to everyday life. Includes thorough discussion of frequently misidentified types useful for readers who seek more precise differentiations between specific types.

Riso, Don Richard and Russ Hudson, The Wisdom of the Enneagram, New York: Bantam Books, 1999. A lucid analysis of the personality types that highlights an original approach to working with the Enneagram for spiritual transformation. Information on the types is organized to facilitate in-depth study.

Riso, Don Richard and Russ Hudson, Personality Types, rev. ed., Boston: Houghton-Mifflin Co., 1996.
A complete text of Enneagram theory and descriptions, including an extensive history of the Enneagram. A classic in the field, this book introduced a groundbreaking map of the way each type can evolve or unravel, outlining the highest to lowest functioning states.

Riso, Don Richard and Russ Hudson, Enneagram Transformations, Boston: Houghton-Mifflin Co., 1993.A handy compendium of affirmations specifically designed for each type.


The Enneagram Institute, World Headquarters

The International Enneagram Association


If you have taken the free quiz and would like a more comprehensive, scientifically validated personality test, the Enneagram Institute website has several different self-administered tests:

Information on scientific validation of the Riso/Hudson type descriptions and the EI tests is on the website,

Further information about ongoing research validating the Enneagram types is also available:



The Enneagram Journal
A professional. peer-reviewed journal published annually by the International Enneagram Association. A forum for constructive dialogue and discussion about Enneagram-related topics including theory, research, and book reviews.

Enneagram Monthly
An independent monthly publication with academic and popular articles focusing on the study of the Enneagram and Enneagram events around the world. EM has collected an extensive archive of over a decade of articles and research.

Always remember that when the shadows in ourselves are
touched by the light of awareness, they become doors
through which grace transforms our lives.

~ Don Richard Riso, Enneagram Transformation

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