The chapters included in this book examine various aspects of the disclosure and concealment phenomena, whether from client or therapist perspective. Contributions examine the relationship of therapist self-disclosure to alliance and outcome; the phenomenon of therapist self-disclosure in psychodynamic therapy; client concealment and disclosure of secrets in therapy; young adults’ disclosures in psychotherapy and on Facebook; and lying in psychotherapy. Each offers intriguing insights into the disclosure, or lack of disclosure, in psychotherapy, from the therapist or client perspective. This book was originally published as a special issue of Counselling Psychology Quarterly.