BACKGROUND : The term "Wrong-Site Surgery (WSS)" is commonly associated with surgical procedures; however, The Joint Commission (TJC) considers any invasive procedure, not just a surgical procedure, performed on the wrong side, at the wrong site, or on the wrong patient to be a WSS. For anesthesia providers, this means that a wrong-site nerve block (WSNB) also constitutes a WSS and would be considered a sentinel event by TJC. In an attempt to combat WSNB, the American Society of Regional Anesthesia and Pain Medicine published guidelines in 2014 recommending the use of a preprocedural checklist before performing regional blocks. The effectiveness of such a checklist, however, to reduce the occurrence of WSNB has not yet been demonstrated. We hypothesized that the introduction of a preprocedural checklist specific for regional anesthesia would be associated with a lower rate of WSNB procedures. METHODS : A retrospective review was performed to compare the incidence of WSNB 2 years before, to 6 years after the implementation of a preprocedural checklist specific to regional anesthesia. RESULTS : Prior to checklist implementation, 4 WSNB events occurred during 10 123 procedures (3.95 per 10 000 (95% CI 1.26 to 9.53). Following implementation, WSNB events occurred during 35 890 procedures (0 per 10 000 (95% CI 0 to 0.84)); p=0.0023. CONCLUSIONS : Implementation of a regional anesthesia specific preprocedural checklist was associated with a significantly lower incidence of WSNB procedures. While prospective controlled studies would be required to demonstrate causation, this study suggests that for regional anesthesia procedures, a preprocedural checklist may positively impact patient safety.