To evaluate whether, after high thoracic segmental epidural anesthesia, sympathetic blockade spreads caudally beyond sensory blockade, we assessed regional skin temperatures by infrared tele-thermometry in 53 nonpremedicated patients at constant ambient temperature. Either bupivacaine (4.2 ml, 0.75%, n = 10) or an equal volume of saline (placebo, n = 10) was injected at the C7-T2 epidural space in a randomized double-blinded fashion. Results were contrasted to those observed after midthoracic (T6-T9, n = 13) and lumbar (L2-T12, n = 10) epidural injection of an identical dose of bupivacaine or saline (n = 10). Despite restriction of sensory block to the upper thorax with high thoracic epidural anesthesia, skin temperatures increased significantly (P< 0.05vs. saline) on the foot (great toe: +1.2° C ± 2.9 SD; little toe: +0.9° C ± 2.6) and hand (thumb: +2.0° C ± 4.0, digit 5: +2.9° C ± 4.2) but decreased after saline. Midthoracic injection also increased significantly skin temperature on the foot (great toe: +4.0° C ± 4.9; little toe: +3.6° C ± 4.8) but not on the hand. In contrast, with lumbar epidural anesthesia, skin temperature increased significantly on the foot (great toe: +8.5° C ± 2.5; little toe: +8.6° C ± 2.8) but decreased significantly on the hand (thumb: −3.1° C ± 2.1; digit 5: −2.8° C ± 2.5). Whereas the increase in foot skin temperature was greater after lumbar than after high (P< 0.003) or midthoracic (P< 0.03) segmental epidural anesthesia, there was no difference (P= 0.6) in foot skin temperature change between high and midthoracic injection. On the trunk, skin temperatures either did not change or decreased significantly even within analgesic dermatomes. Thus, a substantial, albeit submaximal, increase in foot skin temperature was observed with thoracic epidural anesthesia. Assuming that increased foot skin temperatures reflect diminished sympathetic outflow, we conclude that mid- and even high thoracic segmental epidural anesthesia involving only a few dermatomes can result in a widespread sympathetic block that includes the most caudal parts of the sympathetic nervous system.