We present two cases of severe pain due to critical limb ischemia (CLI) treated with automated intermittent bolus infusion for continuous sciatic nerve blocks. Case 1: A 32-year-old man had severe lower extremity ischemic pain due to Fontaine grade IV peripheral vascular disease. The pain did not respond to systemic analgesics. A popliteal nerve catheter was placed under ultrasound guidance. After confirming the effect of continuous infusion of ropivacaine from the catheter unsatisfactory, automated intermittent with patient-controlled bolus administration was started. His pain was controlled well. Case 2: A 52-year-old man had severe foot pain due to Buerger's disease. Bypass surgery and angioplasty failed to improve his symptoms. Even after the amputation of superficial fibular nerve, deep fibular nerve and tibial nerve, his pain persisted. The continuous popliteal sciatic nerve block was started. As continuous infusion did not relieve his pain, automated intermittent with patient-controlled bolus administration was started. However even with this technique, his pain was not relieved well. In some patients whose severe pain due to CLI could not be managed well, automated intermittent bolus infusion of local anesthetics from peripheral nerve catheter may provide better analgesia than continuous infusion.