Low-dose bupivacaine can limit the spinal block level with minimal hemodynamic effects and yield a rapid recovery, but sometimes it may not provide adequate anesthesia for surgery. Dexmedetomidine, a selective α2-adrenoreceptor agonist, was shown to be a potent antinociceptive agent when given intrathecally in animals and humans. The purpose of this study was to evaluate the adjuvant effects of intrathecal dexmedetomidine in elderly patients undergoing transurethral prostate surgery with low-dose bupivacaine spinal anesthesia. Fifty-four patients undergoing transurethral prostate surgery were randomized into two groups receiving either dexmedetomidine 3 µg ( n =27) or normal saline ( n =27) intrathecally with 6 mg of 0.5% hyperbaric bupivacaine. The characteristics of the spinal block and postoperative analgesic effects were evaluated. The peak block level was similar for the two groups. However, the dexmedetomidine group demonstrated a faster onset time to the peak block and longer duration of spinal block than the saline group ( p <0.01). The motor block scales at the time of peak sensory block and regression of 2-sensory dermatomes were higher in the dexmedetomidine group than in the saline group ( p <0.001). There was less analgesic request and the time to the first analgesic request was longer in the dexmedetomidine group than in the saline group (each 487, 345 min, p <0.05). Dexmedetomidine 3 µg when added to intrathecal bupivacaine 6 mg produced fast onset and a prolonged duration of sensory block and postoperative analgesia in elderly patients for transurethral surgery. However, recovery of motor block could be delayed in dexmedetomidine-added patients.