Eye movement desensitization and reprocessing (EMDR) has emerged as a promising new treatment for trauma and other anxiety-based disorders. However, the neurobiological mechanism of EMDR has not been well understood. This study reports changes in the resting regional cerebral blood flow after successful EMDR treatment in two patients with posttraumatic stress disorder (PTSD). Brain 99mTc-ECD-SPECT (Technetium 99m–ethyl cysteinate dimmer–single photon emission computerized tomography) was performed before and after EMDR, and, in addition, a pre- and posttreatment comparison was made with 10 non-PTSD participants as a control group. After EMDR, cerebral perfusion increased in bilateral dorsolateral prefrontal cortex and decreased in the temporal association cortex. The differences between participants and normal controls also decreased. Changes appeared mainly in the limbic area and the prefrontal cortex. These results are in line with current understanding of neurobiology of PTSD. EMDR treatment appears to reverse the functional imbalance between the limbic area and the prefrontal cortex.