Forty primigravidas were given a bilateral paravertebral lumbar sympathetic block during stage I of labor using 10 cc of 0.5% bupivacaine and 1:200,000 epinephrine on each side. Good analgesia was obtained in 38 patients with maximal effect 7.5 +/- 3 minutes after blockage. Maternal mean blood pressure and pulse were unchanged, fetal well-being was not compromised, and labor progressed rapidly. Twenty-eight patients delivered prior to resolution of the block, while in the remaining 12 patients pain returned before delivery with analgesia having lasted 283 +/- 103 minutes. In the former 28 patients, analgesia for expulsion was provided by pudendal, saddle block, or infiltration analgesia, whereas continuous lumbar epidural or caudal analgesia was utilized when remission preceded stage II. In comparison to continuous lumbar epidural analgesia, the procedure is technically more difficult, generally more painful, and requires a second anesthetic for delivery. It is concluded that bilateral paravertebral lumbar sympathetic block with bupivacaine provides reliable analgesia of long duration with a low incidence of undesirable side effects. However, its primary usefulness is in cases where continuous lumbar epidural analgesia is refused or contraindicated.