The introduction of surgical safety checklists is often seen as a milestone accomplishment for the patient safety field, based on impressive reductions in mortality and complications shown in early international studies. More recently, a large trial in Ontario failed to show significant improvements following mandatory checklist adoption. However some concerns were raised related to methodological limitations, such as a lack of a comprehensive program for implementation. This study examined the effects of the Keystone Surgery program, a statewide effort in Michigan hospitals to introduce a surgical safety checklist along with a comprehensive unit-based safety program. Using Medicare claims data, no differences were found in adjusted 30-day mortality, complication rates, reoperations, or readmissions for hospitals participating in Keystone Surgery. Unlike the prior Ontario study, this study assessed outcomes up to 3 years following implementation and included a standardized and comprehensive implementation strategy. These results cast further doubt on the power of surgical safety checklists to improve outcomes when implemented in non-research settings.