So as to determine the effects of some factors on the duration of bupivacaine spinal anaesthesia, a prospective controlled study was carried out on 152 ASA I or II patients. They were randomly allocated to six groups. The patients of group I were given 4 ml of 0.5% bupivacaine at 27 degrees C. The patients of group II were given 4 ml of a mixture including 3 ml of 0.5% bupivacaine, 1 ml fentanyl in 1 ml of 10% dextrose solution. The group III was given 4 ml of a mixture including 3 ml of 0.5% bupivacaine, 0.20 mg adrenaline. The group IV was given 4 ml of a mixture including 3 ml of 0.5% bupivacaine, 0.15 mg clonidine. The patients of group V were given 4 ml of 0.5% bupivacaine at 20 degrees C and those of group VI were given 4 ml of 0.5% bupivacaine at 5 degrees C. There is significant difference between regression times of sensory analgesia of group II and group I, group IV and group III, group VI and group V. The choice of product to lengthen analgesia in spinal anaesthesia depends on the use of each anaesthesist, the characteristic of patients and the duration of surgery.