Posttraumatic stress disorder (PSTD), classified as an anxiety disorder, has become increasingly important because of wars overseas, natural disasters, and domestic violence. After trauma exposes the victim to actual or threatened death or serious injury, 3 dimensions of PTSD unfold: (1) reexperiencing the event with distressing recollections, dreams, flashbacks, and/or psychologic and physical distress; (2) persistent avoidance of stimuli that might invite memories or experiences of the trauma; and (3) increased arousal. Traumatic events sufficient to produce PTSD in susceptible subjects may reach a lifetime prevalence of 50% to 90%. The actual lifetime prevalence of PTSD among US citizens is approximately 8%, with the clinical course driven by pathophysiologic changes in the amygdala and hippocampus. Comorbid depression and other anxiety disorders are common. General principles of treatment include the immediate management of PTSD symptoms and signs; management of any trauma-related comorbid conditions; nonpharmacologic interventions including cognitive behavioral treatment; and psychopharmacologic agents including antidepressants (selective serotonin reuptake inhibitors most commonly), antianxiety medications, mood stabilizing drugs, and antipsychotics. This review of PTSD will provide the reader with a clearer understanding of this condition, an increased capacity to recognize and treat this syndrome, and a greater appreciation for the role of the internist in PTSD.