Insertion and maintenance of an interscalene catheter is technically challenging using lateral or anterior approaches. We report a technique to provide continuous brachial plexus blockade through a 48-h infusion of ropivacaine 0.1% (5 mL/h with a 5 mL bolus dose, 20-min lockout interval) using a catheter inserted with cannula-over-needle technique on the posterior side of the neck in 120 patients undergoing shoulder surgery. All catheters were successfully placed. There were no technical complications (impossibility to thread catheter, accidental vascular, epidural or subarachnoid location), catheter dislodgment, or analgesic solution leakage. Dysphonia, Horner's syndrome, and difficulty breathing were observed in 12 patients, four patients, and one patient, respectively. One patient complained of minor paresthesia that spontaneously resolved. Three patients complained of cervical pain. Pain scores as well as ropivacaine requirement via a patient-controlled analgesia device were low. Evaluation of acute and nonacute complications in a large-size study is needed to compare efficacy and safety of this approach with existing techniques.