Objective: The aim of the present study was to compare the duration of time interval in the onset of motor and sensorial blocking effects of bupivacain and alkalinised bupivacain in patients whom underwent combined ischiatic-femoral blockage in arthroscopic knee surgery. Methods: Overall, 40 patients aged between 20-60 years with ASA I/II scores randomized into 2 groups and included in our study. Ischiatic nerve blockage was performed by using 20 ml 5% bupivacain+0,1 ml 0,9% NaCl and femoral nerve blockage was performed by using 20 ml 0,5% bupivacain+0,1 ml 0,9% NaCl in patients included in Group 1. Ischiatic nerve blockage was performed by using 20 ml 0,5% bupivacain+0,1 ml 8,4% sodium bicarbonate and femoral nerve blockage was performed by using 20 ml 0.5% bupivacain+0,1 ml 8,4% sodium bicarbonate in patients included in Group 2. Results: S1-2 dermatom region located at the posterior thigh surface was used for sensorial evaluation of the ischiadic nerve and L2-4 dermatom region located at the anterior thigh surface was used for sensorial evaluation of the femoral nerve by using the pinprick test. Motor blockage was evaluated by using the Bromage scale. Data corresponding to the beginning and 1st, 3rd, 5th, 10th, 15th, 20th and 30th minutes of the study were recorded. Conclusions: In conclusion, no significant differences were detected in the duration of onset of motor and sensorial blockage effects of bupivacain and alkalinised bupivacain in patients who underwent combined ischiatic-femoral blockage in arthroscopic knee surgery.