Research Methods and Procedures:We carried out a systematic search of English-language literature on WLS in MEDLINE and the Cochrane Library. Key words were used to narrow the field for a selective review of abstracts. Data extraction was performed, and evidence categories were assigned according to a grading system based on established evidence-based models. Results: We assessed types of WLS, recommended guidelines for appropriateness, developed strategies for medical error reduction, established criteria for credentialing of systems and practitioners, and specified research needed for the future. Discussion: Surgeon training, credentialing, and type of surgery performed were identified as key factors in patient safety. Other important issues in the delivery of best practice care included appropriate patient selection; use of a multidisciplinary treatment team; facility staffing, equipment, and administrative support; and early recognition and proper management of complications.