The level of sensory blockade in spinal anesthesia is determined by the distribution of local anesthetics within cerebrospinal fluid (CSF) which is affected by the density of local anesthetics. Temperature is one of the factors which can influence the density of local anesthetics. The level of sensory blockade in spinal anesthesia may be altered by the density change of local anesthetics and by the time needed for thermal equilibration in CSF, depending on the storage temperature of local anesthetics. A study was conducted at Inchon Severance hospital on 20 elective surgery patients under spinal anesthesia, to compare the clinical differences between two groups stored at different temperatures. Group I was used 0.5% plain bupivacaine 3 ml (15 mg) stored in a refrigerator for longer than 24 hours and group II was used that stored in operating room temperature. The results were as follows : The level of sensory blockade in group II was significantly higher than that of group I, 3 minutes after spinal anesthesia by segmental level of sensory loss to pinprick test. The degree of motor blockade was significantly greater by Bromage scale in group II than in group I at 2 minutes after spinal anesthesia, but no significant difference was observed after 5 minutes. When 15 minutes elapsed, the complete motor blockade of lower extremities was observed in both groups. The onset of sensory block was significantly faster in group II(3.1+/-0.2 min) than in group I (5.2+/-0.5 min). The onset of maximum sensory block was also significantly faster in group II(9.5+/-0.5 min) than in group I (14.0+/-1.5 min). The maximum sensory block level was significantly higher in group II(T6.7+/-0.3 dermatome) than in group I (8.2+/-0.3 dermatome). However, the regression time was not significantly different between group I (122.0+/-3.8 min) and group II (117.2+/-6.0 min). The above results showed that when 0.5% plain bupivacaine stored in room temperature was used in spinal anesthesia, gave higher level of sensory blockade and faster onset than that kept in a refrigerator, which may due to the time difference needed for thermal equilibration in CSF.