Background Standard superficial temporal artery-middle cerebral artery (STA-MCA) bypass surgery is an effective treatment for moyamoya disease, but recent evidence suggests that postoperative cerebral hyperperfusion can occur. In this study, the trendline of changes in regional cerebral blood flow (rCBF) after surgery were continually monitored near the site of anastomosis in order to investigate both the efficacy of the procedure for improving rCBF and the possible riskof hyperperfusion.Methods Standard STA-MCA bypass surgery was performed on 13 patients, rCBF was measured continually using laser Doppler flowmetry (LDF) until the 5th day after the operation with the LDF probe implanted adjacent to the area of the anastomosis. The trendline of rCBF changes postoperatively was recorded for the analysis performed using SPSS 13.0.Results The baseline LDF value of cortical rCBF was (84.68±14.39) perfusion unit (PU), which was linear relative to absolute perfusion volume before anastomosis and (88.90±11.26) PU immediately after anastomosis (P >0.05). The value changed significantly from before to after anastomosis (P <0.05); it was (417.72±21.35) PU on the 1st day after surgery, and (358.99±18.01) PU, (323.46±17.38) PU, (261.60±16.38) PU and (375.72±18.45) PU on the following 4 days,respectively. The rCBF decreased gradually from the 2nd day until the 4th postoperative day, but still was at a high level (P<0.05). However, on the 5th postoperative day the rCBF increased again to the second highest level, which was significantly different compared with the baseline value (P<0.05), but not significantly different compared with the values on the other 4 days (P>0.05).Conclusions STA-MCA anastomosis improves the cerebral blood supply significantly in the early stage after surgery,however, the risk of symptomatic hyperperfusion may exist, which may possibly occur on the 1st day and 5th day after surgery. A LDF is useful for postoperative monitoring for both the efficacy of bypass and possible risk of neurologic deterioration or bleeding from hyperperfusion.