154 patients scheduled for arthroscopic rotator cuff repair were randomized to either a single-shot interscalene brachial plexus block (ssISBPB). patient-controlled interscalene infusion analgesia (PCIA) postoperatively, or to a control group not administered additional analgesia. The purpose was to compare pain scores from 1 hour to 48 hours after surgery. There were marked differences in pain score trajectory between the two intervention groups, with significantly lower pain at 1 and 2 hours in the ssISBPB group compared to the PCIA group, but significantly lower pain in the PCIA group compared to the ssISBPB group at 12 and 24 hours postoperatively.