Intervillous blood flow was measured using a133Xe clearance technique during the first stage of labor in 9 parturients with severe preeclampsia before and after lumbar epidural analgesia. Analgesia was produced with 10 ml of 0.25% bupivacaine. After the lumbar epidural block the intervillous blood flow significantly improved, suggesting that epidural analgesia is the obstetric analgesic method of choice in cases of severe preeclampsia.