Background : One of the most important physical properties affecting the level of analgesia after intrathecal administration of a local anesthetic is baricity. This study was done to compare the distribution of 0.5% tetracaine in 5% glucose solution and in 10% glucose solution. Methods : Tetracaine 2.6 ml (0.5% with 5% glucose or 10% glucose) added with 0.1% epinephrine 0.2 ml was administered to each of 20 patients. All patients' heights were within 160-170 cm. The cephalad spread of analgesia, the degree of motor block in the legs and hemodynamic values were assessed at 2-min intervals for the first 10 min and then at 5-min intervals until 30 min. Results: In the 5% glucose and 10% glucose solutions. the maximum sensory level was T5.4 and 74,3, the maximum sensory block time was 128.1 min and 118.2 min and the time to complete motor block was 5.4 mill and 5.2 min respectively. It was not statistically significant between groups. But T 8.1 (vs T 9.6 in the 5% glucose solution) of initial sensory level measured at 4 min after injection of drug was significantly higher (P < 0.05) in the 10% glucose solution. Maximum hemodynamic changes from the baseline were not different in two groups. Conclusions: Tetracaine 0.5% with 5% glucose or 10% glucose solutions showed similar distribution in the cerebrospinal fluid. (Korean J Anesthesiol 2000; 38: 58∼62)