BACKGROUND The pain control efficacy, postoperative opioid requirements, and costs among patients undergoing major shoulder surgery using different perioperative analgesia modalities have been topics of active debate. Several studies have compared periarticular injection (PAI) to interscalene block (ISB) in shoulder arthroplasty, but there is a paucity of data comparing them in arthroscopic rotator cuff repair. METHODS Patients aged 18-80 years with full-thickness rotator cuff tears and undergoing primary arthroscopic rotator cuff repair at 2 different shoulder centers were screened and subsequently randomized to receive either periarticular injection (PAI) of liposomal bupivacaine mixed with 0.25% bupivacaine (n = 41) or single-shot interscalene nerve block (ISB) (n = 36). Visual analog scale (VAS) pain scores, oral morphine equivalent (OME) use, Single Assessment Numerical Evaluation (SANE) scores, and costs were collected. Differences with P