EHR implementations span multiple years. It is critical that while the new system is being implemented, the existing applications continue to function effectively in order to support operations and patient care. They must be maintained and enhanced to meet critical business needs. All of this requires an effective staffing and leadership strategy for those whose focus during the time of transition will be on the support and maintenance of these “legacy," or core, systems. Three years ago, Houston Methodist embarked on a journey to replace their existing clinical systems with an integrated EHR. A key success factor has been the effective management of the legacy application portfolio and the staff and leadership who are responsible for its effective functioning. This presentation will detail the approach taken at Houston Methodist to meet this challenge and will provide lessons learned which will be of interest to any health system that is planning or currently engaged in a large-scale EHR implementation.