Eye Movement Desensitization and Reprocessing (EMDR) is an efficacious and efficient treatment for posttraumatic stress disorder (PTSD). This article provides a brief overview of the findings of 20 controlled-outcome studies and describes Shapiro's Adaptive Information Processing model. This model posits that pathology results when distressing experiences are processed inadequately and hypothesizes that EMDR accelerates information processing, resulting in the adaptive resolution of traumatic memories. A detailed description of the eight phases of treatment highlights the procedures, assumptions, and clinical observations that currently guide EMDR clinical practice. A case study, with an in-session transcript, illustrates the application of EMDR to address the past events that have laid the groundwork for dysfunction, the present circumstances that elicit distress, and skills acquisition needed for adaptive functioning. © 2002 Wiley Periodicals, Inc. J Clin Psychol/In Session 58: 933–946, 2002.