The Clinical & Systems Transformation (CST) project aims to transform healthcare in Vancouver by standardizing clinical practice and creating a shared electronic health record across three large health organizations. The evaluation of such a complex, multi-organization, multi-phase, billion-dollar project is much like navigating a ship through uncharted waters. Since its inception in 2013, the project itself has gone through multiple changes in approach, each time requiring us to adjust our evaluation strategy, much like captain on a ship's bridge responds to changing winds, turning tides, and previously unforeseeable obstacles. In this session we will share lessons learned from our voyage so far, including how we've applied complexity and systems thinking to be responsive to those changes while also ensuring we stay on course to deliver an evaluation that is useful to a diverse range of stakeholders throughout the journey.