This report describes the removal of large putaminal hematomas using an endoscopic surgical technique with a 3 mL syringe barrel as a conduit. The 3 mL syringe barrel (outer diameter, 8mm) was used as an endoscopic sheath and a 14 F Foley catheter was modified as an endoscopic stylet. With the patient in the supine position, we used an entry point on the temporal scalp, ipsilateral to the hematoma. From January 2005 to January 2006, 25 patients with large putaminal hematomas underwent endoscopic surgery. The inclusion criteria for endoscopic surgery were: (i) putaminal hemorrhage with hematoma volume>40 mL; and (ii) a Glasgow Coma Scale (GCS) score of 3 to 12 with a focal neurological deficit. The exclusion criteria were: (i) a hemorrhage due to tumor, trauma, aneurysm, or arteriovenous malformation; (ii) non-putaminal hemorrhages; and (iii) coagulopathy. No surgical complications occurred. The time from the onset of symptoms to surgery ranged from 1 hour to 5 hours (median, 2 hours). Preoperative hematoma volumes ranged from 40 mL to 180 mL (median, 78 mL); postoperative hematoma volumes ranged from 2 mL to 16 mL (median, 6 mL). Therefore, 90 to 97% (median, 93%) of the hematoma was evacuated. The preoperative GCS scores ranged from 3 to 12 (median, 8); the postoperative GCS scores ranged from 6 to 15 (median, 12). The mortality rate was 16%; one year postoperatively, the mean Glasgow Outcome Scale score was 2.7. Thus, endoscopic removal of large putaminal hematomas is safe, effective, and minimally invasive. The new endoscopic sheath is inexpensive, disposable, and easy to use.