Background and objectives: this study was done to evaluate the effect of adding dexmedetomidine and clonidine 1µ/kg to levobupivacaine 0.5% with the sciatic nerve block. Patients and methods: Sixty patients scheduled for elective lower limb surgery were randomly allocated into 3 groups to receive ultrasound guided sciatic nerve block with ultrasound guided femoral nerve block to avoid tourniquet pain as follows: Group L received 20 ml levobupivacaine 0.5% for sciatic nerve block and 20 ml levobupivacaine 0.5% for femoral nerve block. Group LD received 20 ml levobupivacaine 0.5% PLUS dexmedetomidine 1µ/kg for sciatic nerve block and 20 ml levobupivacaine 0.5% PLUS dexmedetomidine 1µ/kg for femoral nerve block and Group LC received 20 ml levobupivacaine 0.5% PLUS clonidine 1µ/kg for sciatic nerve block and 20 ml levobupivacaine 0.5% PLUS clonidine 1µ/kg for femoral nerve block. Onset and duration of sensory block, onset and duration of motor block, hemodynamic parameters and quality of operative conditions were assessed. Results: Onset of sensory and motor block in group LD and group LC were significantly faster than that of group L. The duration of sensory and motor block in group LD and group LC were significantly longer than group L. There was a significant decrease in heart rate and mean arterial blood pressure in group LD and group LC in comparison with group L. The quality of operative conditions was better with dexmedetomidine than with clonidine. Conclusion: adding 1µ/kg dexmedetomidine and clonidine to levobupivacaine for sciatic nerve block leads to more rapid onset and prolongs the duration of sensory and motor block and improves quality of block.