The use of opioids for spinal anesthesia increases the anesthetic quality, reduces side effects and also has advantages for the postoperative analgesia. The aim of this study was to evaluate the effects of subarachnoid % 0.5 hyperbaric bupivacaine (B) alone or combined with 10 or 20 mu g fentanyl (F) on the anesthetic properties for cesarean section and newborn. 45 patients were randomized to three groups to receive 1.8 ml anesthetic drug for spinal anesthesia. GI (n=15) received B, GII (n=15) 10 mu g F+B, GIII (n=15) 20 mu g F+B. The onset of sensory blok at T4 level, maximum anesthetic level and the onset time, the level of the motor block, duration of effective analgesia, use of total i.v. fluids and ephedrine, relaxation at the operative area, side effects, umblical cord blood gases, Apgar and neurological and adaptive capasity scores of the newborn were compared among the groups. We conclude that compared to control group, the addition of fentanyl to hyperbaric bupivacaine leads to a decrease in local anesthetic doses and so to a decrease in the incidence of side effects and postoperative analgesic consumption. 7 mu g B+20 mg F seems to be the preferable combination for that reasons.