Mothers given an epidural rather than parenteral opioid labor analgesia report less pain and are more satisfied with their pain relief. Analgesic method does not affect fetal oxygenation, neonatal pH, or 5-minute Apgar scores; however, neonates whose mothers received parenteral opioids require naloxone and have low 1-minute Apgar scores more frequently than do neonates whose mothers received epidural analgesia. Epidural labor analgesia does not affect the incidence of cesarean delivery, instrumented vaginal delivery for dystocia, or new-onset long-term back pain. Epidural analgesia is associated with longer second-stage labor, more frequent oxytocin augmentation, hypotension, and maternal fever (particularly among women who shiver) but not with longer first-stage labor. Analgesic method does not affect lactation success. Epidural use and urinary incontinence are associated immediately postpartum but not at 3 or 12 months. The mechanisms of these unintended effects need to be determined to improve epidural labor analgesia. (Am J Obstet Gynecol 2002;186:S69-77.)