The aim of the study was to compare the block characteristics and clinical effects of dextrose added to levobupivacaine solutions at different concentrations to provide unilateral spinal anaesthesia in lower extremity surgery.This prospective, randomised, double-blind study comprised 75 ASA I-II risk patients for whom unilateral total knee arthroscopy was planned. The patients were assigned to three groups: in Group I, 60mg dextrose was added to 7.5mg of 0.5% levobupivacaine, in Group II, 80mg and in Group III, 100mg. Spinal anaesthesia was applied to the patient in the lateral decubitus position with the operated side below and the patient was kept in position for 10min.The time for the sensorial block to achieve T12 level was slower in Group I than in Groups II and III (p<0.05, p<0.00). The time to full recovery of the sensorial block was 136min in Group I, 154min in Group II and 170min in Group III. The differences were statistically significant (p<0.05). The mean duration of the motor block was 88min in Group I, 105min in Group II, and 139min in Group III and the differences were statistically significant (p<0.05). The time to urination in Group I was statistically significantly shorter than in the other groups (p<0.00).The results of the study showed that together with an increase in density, the sensory and motor block duration was lengthened. It can be concluded that 30mgmL(-1) concentration of dextrose added to 7.5mg levobupivacaine is sufficient to provide unilateral spinal anaesthesia in day-case arthroscopic knee surgery.