BACKGROUND: Cerebral blood flow (CBF) is important in the management of cerebrovascular diseases. Surgical manipulation may compromise the appropriate interpretation of postoperative CBF changes, but the effects are not well understood. Objective: To investigate the effect of surgical manipulation on postoperative CBF in a setting of prospective randomized comparison of 2 irrigation fluids during surgery. Methods: Twenty patients undergoing the clipping of unruptured cerebral aneurysms through the pterional approach were randomly assigned to use of Artcereb, an artificial cerebrospinal fluid, or physiological saline as irrigation fluid. Postoperative CBF and clinical conditions were evaluated 3 times in the first 7 to 10 postoperative days. Results: Postoperative CBF decreased by 10 to 15% on the first postoperative day in the ipsilateral inferior frontal gyrus, where surgical manipulation may be greatest. CBF reduction was less in regions remote from the surgical site and later in the follow-up periods. Selection of irrigation fluid did not influence postoperative CBF significantly, although postoperative clinical conditions may be better using Artcereb. Conclusion: Postoperative CBF changes due to surgical manipulation should be considered in patients whose hemodynamic conditions are important for appropriate management.