Purpose: The purpose of this study was to compare the effectiveness of postoperative pain control by intravenous patient-controlled analgesia (IV) to the effectiveness of postoperative pain control by continuous intra-lesional infusion of local anesthetics (IL) with or without an interscalene brachial plexus block (ISB) after arthroscopic shoulder surgery. Materials and Methods: We designed this prospective randomized case-controlled double-blind study, and allocated 84 consecutive patients to four groups according to postoperative analgesic method, i.e., Group IV, Group ISBIV, Group IL, and Group ISB-IL after arthroscopic shoulder surgery. Postoperative pain, side effects and supplemental analgesics were recorded at 1 hour and then at every 8 hours for 2 days. Result: The demographic and clinical characteristics of four groups were identical statistically. Interscalene block (Group ISB-IV, Group ISB-IL) was found to be effective at relieving pain and at reducing supplemental analgesic amounts at 1 and 8 hours postoperatively (p<0.05). Patients in the Group ISB-IL had less pain at 16 and 48 hours postoperatively than the other groups (p<0.05). Continuous intra-lesional infusion (Group IL, Group ISB-IL) was superior in reducing analgesic-related side effects (p<0.05). Conclusion: This study suggests that a combination of an interscalene brachial plexus block and continuous intralesional infusion of ropivacaine is an effective and safe method of postoperative pain control in patients after arthroscopic shoulder surgery.