BACKGROUND: Tourniquet pain is probably mediated by C-fiber. The ability of fentanyl to interrupt this nociceptive conduction was studied by administering either fentanyl or saline intrathecally along with hyperbaric bupivacaine for spinal anesthesia. METHOD: The incidence of tourniquet pain was evaluated in 60 patients having orthopedic surgery of the lower extremities during spinal anesthesia by administering either 30 mcg fentanyl (group 2) or saline (group 1) along with 0.5% hyperbaric bupivacaine 10 mg. We measured the maximal sensory spread of analgesia to pinprick, the incidence of tourniquet pain, and the sensory anesthesia to pinprick at the onset of tourniquet pain. RESULTS: The average maximal sensory spread of analgesia was the same in both groups (T9). The incidence of tourniquet pain was significantly greater in group 1 (33%) than in group 2 (10%). The sensory levels of anesthesia at the onset of tourniquet pain were not different in two groups. CONCLUSIONS: Intrathecal fentanyl was effective against tourniquet pain for 2 hours of the orthopedic surgery of the lower extremities.