The interconnected theory of Logotherapy and Existential Analysis has been internationally recognized for decades as an empirically supported humanistic school of psychotherapy. One of Viktor E. Frankl's numerous contributions to the field is a deliberately balanced approach to theory and applied practice within this framework, which he focuses on a variety of topics. On the Theory and Therapy of Mental Disorders will, for the first time, allow English speakers to read Frankl's seminal work on mental disorders in the original. This work presents Viktor Frankl's philosophical views as applied to his psychiatric practice, offering a unique perspective to therapy. The English translation features an introduction and commentary by James M. DuBois, a leading Frankl scholar, as well as a new glossary of terms and notes updating the medication information for the twenty-first century.