Purpose: To compare the median effective dose (ED50) of hyperbaric bupivacaine with fentanyl 25 µg in combined spinal epidural anesthesia (CSEA) with and without epidural volume extension (EVE) for Caesarean section, using colloid [6% hydroxyl ethyl starch (HES)(200/0.5)] for EVE. Clinical features: 120 subjects scheduled for an elective caesarean section (ASA grade I or II, 20-40 years of age, average height of 145-165 cm and ±20% of the ideal body weight) were randomized to receive either CSEA with EVE by 6% HES (EVE group) or no EVE (NEVE group). Using a double-blinded, up-down sequential technique; varying doses of bupivacaine with fentanyl 25 µg were administered.