Rapid response teams (RRTs) have been implemented at hospitals worldwide, despite mixed results in their effectiveness. The aim of this study was to compare expected mortality rates with mortality rates following RRT implementation, adjusted for hospital case mix. Of 56 hospitals that participated in this project and had complete data, only four showed lower-than-expected mortality rates and two showed higher-than-expected mortality, suggesting RRT may not reduce mortality rates as much as earlier studies have reported.