['Embolization before surgical resection of tumors has been demonstrated to reduce intraoperative blood loss, but the optimal time that should elapse between embolization and tumor resection has not been established. We evaluated whether immediate surgical resection (< or =24 h) after embolization or delayed surgical resection (>24 h) was more effective in minimizing intraoperative blood loss.', 'We retrospectively analyzed the records for 50 patients with meningiomas who underwent preoperative embolization between 1993 and 1999. We divided the patients into two groups, i.e., those who underwent surgical resection of their meningiomas < or =24 hours after embolization and those who underwent surgery more than 24 hours after embolization. The extent of embolization, intraoperative blood loss, duration of surgery, and length of the hospital stay were compared for the two groups. Postoperative pathological specimens were examined for assessment of the extent of vascularity and necrosis caused by embolization.', 'Intraoperative blood loss was greater for the immediate group than for the delayed group (29% with blood loss of >1000 ml [median, 475 ml] versus 0% with blood loss of >700 ml [median, 337.5 ml]; P = 0.01). There were no statistically significant differences between the groups with respect to tumor volume, extent of embolization, degree of devascularization, necrosis, duration of surgery, or length of the hospital stay.'] Does delayed surgical resection reduce intraoperative blood loss for embolized meningiomas?