Background: Bier's block is a simple, rapid and effective method with very high success rate. However it has some drawbacks as great liability to systemic toxicity, tourniquet pain, and post- tourniquet deflation rapidly evolving postoperative pain. Objective: To reveal the effect of adding Ketamine to lidocaine on the characters of Bier's block. Methods: Fifty adult both sex patients, with physical status of ASA I and II and prepared for minor elective below elbow surgical procedures were enrolled in this study. Patients were randomly divided into two equal groups (25 patients for each one); Lidocaine group that received 3 mg/kg lidocaine and Lidocaine/Ketamine group that received 3 mg/kg lidocaine plus 0.1mg/kg ketamine. The primary outcomes were the characters of Bier's block (onset, potency, Tourniquet tolerance time, recovery time after tourniquet deflation, time to the 1st ask and the amount of the consumed analgesic in the 1st 24 hrs post-operatively) and secondary outcomes were the hemodynamic and respiratory changes, beside the rates of the associated side effects. Results: Ketamine significantly improved the characters of Bier's block (i.e. enhanced the block onset, increased intraoperative anesthetic potency, prolonged tourniquet tolerance time, prolonged the time to time to the 1st ask and decreased the amount of the consumed analgesic after surgery), without causing significant hemodynamic changes or any serious side-effects. Conclusion: Ketamine is a suitable adjuvant to local anesthetics. It improves the characters of Bier's block without causing significant hemodynamic changes or any serious side-effects.