A prospective, randomised study was performed to investigate the influence of temperature on sensory blockade in spinal anaesthesia. Three ml of plain bupivacaine 0.5% were injected intrathecally at either 4 degrees C, room temperature, or 37 degrees C. There were 10 patients in each group, who were kept sitting for 2 minutes after injection. The maximum level of sensory blockade was significantly higher (p less than 0.01) in the group who received the solution adjusted to 37 degrees C, and variability of level was smaller (p less than 0.05). Time to two-segment regression was shorter in the 37 degrees C group than in the 4 degrees C group (p less than 0.05). Hypotension required administration of ephedrine more often in the 37 degrees C group (p less than 0.05). It is concluded that the use of plain bupivacaine 0.5% adjusted to 37 degrees C results in a higher and more predictable sensory blockade.