Background : Periarterial sympathectomy ( PAS ) is used to improve blood flow in patients with Raynaud's disease, but the ideal site for PAS and the optimal extent of the procedure remain unknown. We hypothesized that improvements in blood flow occur soon after PAS. Methods : We performed PAS in a 46-year-old female with Raynaud's disease without scleroderma. She had experienced pain in her index finger for several years, and it had proved refractory to conservative treatment. A laser Doppler perfusion imager ( LDPI ) was used to assess the patient's blood flow preoperatively and intra-operatively after sequential PAS of the digital arteries followed by PAS of the radial and ulnar arteries. Results : A significant ( P<0.01 ) improvement in blood flow was seen at 10 minutes after the digital artery in the affected finger was subjected to PAS. PAS of the radial and ulnar arteries ( at the wrist ) did not lead to significant changes in blood flow. The patient reported that her pain had improved at three days after surgery, and it had completely resolved by one postoperative month. Discussion : This study showed that blood flow improves quickly after PAS and that such changes can be detected by LDPI intraoperatively in a non-invasive manner. LDPI might be an effective tool for determining the optimal site and extent of PAS intraoperatively.