Data sources and relevant variables were identified to measure health system efficiency in Canada.1 Phase 2: Measuring the Level and Determinants of Health System Efficiency in Canada (2014) — CIHI applied the conceptual model from Phase 1 to spending and health outcome data, primarily from CIHI and Statistics Canada. [...] Governance CIHI formed an Expert Advisory Committee that included representatives from the ministries of health in Nova Scotia and British Columbia, a methodology expert in multiple case study methods and content experts in health system efficiency to help optimize the relevance, rigour and uptake of the findings of this report. [...] In Phase 2: Measuring the Level and Determinants of Health System Efficiency in Canada, CIHI found significant variations in health system efficiency across the country, with higher scores on average in B. C. than in the rest of Canada, and lower scores on average in Atlantic Canada. [...] On April 1, 2015, in the midst of our recruitment and interview process, the 9 regional health authorities in Nova Scotia underwent a reorganization into the Nova Scotia Health Authority, with no change to the IWK Health Centre.4 This reorganization presented a challenge for our recruitment and interview process, as the 2 health regions we had identified as cases in Nova Scotia ceased to exist and [...] An interview guide (see Appendix A) was developed based on a review and update of the literature collected in the previous 2 phases of the health system efficiency study and in consultation with the Expert Advisory Committee.