BACKGROUND: The distribution of solutions injected into the epidural space has not been well determined. The aim of this study was to compare the difference in extension of sensory blockade between the thoracic and lumbar regions in epidural analgesia. METHODS: Forty-five female patients scheduled for postoperative pain control were enrolled. In group 1 (n = 22), the Tuohy needle was inserted at T6 10 levels and in group 2 (n = 23), it was inserted at T12 L2 levels. The catheter was introduced 3 4 cm into the epidural space and 3 ml of 1.5% lidocaine with epinephrine (1:200,000) was injected. The extension of sensory anesthesia to loss of cold sensation and pinprick test was measured every 5 minute for 15 minutes. RESULTS: Fifteen minutes after epidural injection, the mean sensory block extension in group 1 (7.8 +/- 2.0 dermatomes) was significantly wider than in group 2 (4.7 +/- 2.2 dermatomes) but cranial and caudad spread of sensory blockade in relation to the puncture level was the same in both groups. CONCLUSION: The mean dose of local anesthetic required for analgesia was smaller in the thoracic region than in the lumbar region.