The initial introduction of the World Health Organization surgical safety checklist was associated with impressive improvements in patient safety. However, more recently a study of the government-supported implementation of the checklist in Canada showed no beneficial effect. This study examined the mandated introduction of the surgical safety checklist in hospitals across England and discovered large variation in how the checklist was initially implemented. The most common barrier encountered was resistance from senior clinicians. The authors provide generalizable recommendations to guide the future implementation of improvement efforts. A recent PSNet interview with Dr. Lucian Leape discussed his perspective on the effect and implementation of checklists for patient safety.