Safety culture and work systems influence safety, but it is unclear whether safety improvement efforts should focus on one or both factors. This study sought to improve adherence to the WHO surgical safety checklist and to enhance technical and nontechnical team performance using several safety interventions. One intervention focused on improving safety culture, while another was directed at the work system. Investigators also tested a combined approach. Although both team training and system redesign individually demonstrated improvement, the combined approach was more successful than either individual approach. This finding suggests that in order to truly enhance surgical safety, organizations must invest in both systems and culture interventions.