The use of spinal opioids for postoperative analgesia has gained popularity in recent years. In this study, subarachnoid fentanyl 20 micrograms was evaluated to determine its efficacy for postoperative analgesia, its possible side effects and its effects on the newborn. Sixty ASA class I or II at-term parturients undergoing elective cesarean section were randomly divided into two groups. In one group fentanyl 20 micrograms (0.4 ml) with 0.5% heavy marcaine 2.0 ml was given intrathecally and in the other group only 0.5% heavy marcaine 2.0 ml with CSF 0.4 ml was given intrathecally. The average time for patients in the fentanyl group to demand the first dose of narcotic for pain was 6.8 +/- 3.2 h and in the control group it was 3.9 +/- 1.1 h. The incidences of postoperative nausea and vomiting were higher in the fentanyl group than in the control group. Pruritus was only found in the fentanyl group and amounted to 50%. Early or late respiratory depression was not found in the fentanyl group. During operation, all patients were wakeful and alert. Neonatal condition as determined by 1-min and 5-min Apgar score was satisfactory and showed no significant difference in both groups. Examination on neurobehavior and reflexes done at the baby room showed no abnormality in both groups.