OBJECTIVE: To evaluate postoperative analgesia and patient satisfaction with the continuous interscalene block using 2 bupivacaine concentrations in combination with sufentanil for patients undergoing shoulder rotator cuff repair surgery. MATERIAL AND METHODS: Prospective trial in 43 patients randomized to 2 groups. Group 1 received 0.125% bupivacaine plus 1 microg mL(-1) of sufentanil in continuous infusion at a rate of 7 mL h(-1). Group 2 received an infusion of 0.0625% bupivacaine plus 1 microg mL(-1) of sufentanil at the same rate. Pain was assessed on a visual analog scale (VAS) 2, 4, 6, 12, 24, and 48 hours after surgery. Intravenous ketoprofen and morphine were used to provide rescue analgesia. Morphine and bupivacaine consumption, degree of satisfaction, and the incidence of adverse effects were recorded. RESULTS: Forty-three patients (21 in group 1 and 22 in group 2) were enrolled. Postoperative VAS scores, morphine consumption, and satisfaction were similar in the 2 groups. Bupivacaine consumption was lower in group 2 (P<.005). CONCLUSIONS: Both the tested bupivacaine concentrations for the continuous interscalene block provided similar levels of analgesia after shoulder rotator cuff repair surgery. Reducing the bupivacaine concentration to 0.625% decreased the consumption of local anesthetic without diminishing the quality of analgesia.