Health impact assessment (HIA) has grown exponentially over the past 15 years, with extensive practice now in Australia, UK, US, Thailand, New Zealand, and several other countries. The Society of Practitioners of Health Impact Assessment (SOPHIA) is the only professional organisation dedicated solely to supporting the practice of HIA throughout the world. Founded in 2011, SOPHIA has grown to include several working groups that have produced key documents on HIA, such as practice guides for health equity and mental health in HIA. SOPHIA also has a growing membership base of over 240 practitioners from 14 countries. While SOPHIA continues to grow there are several challenges and priority areas that have been identified in its new strategic plan. Primarily the organisation needs to expand its appeal to a wider, more international audience. Secondly, SOPHIA aims to become a â€˜Centre of Practice' and serve as the primary clearinghouse for relevant HIA resources and opportunities. Additionally, SOPHIA provides high quality resources to build capacity for new and long-term practitioners. All of these activities require long term sustainability of the organisation. The challenges and opportunities of SOPHIA are similar to those of other membership-driven service organisations. As SOPHIA is the only professional association of HIA, it will be necessary for it to grow and adapt to the needs of practitioners, while ensuring sustainability. This presentation will outline the historical development of the organisation, the challenges it currently faces, and engage with the audience to discuss potential solutions to ensure its long term success. Key Messages: 1. SOPHIA is a membership organisation dedicated to developing the capacity of HIA practitioners around the world. 2. SOPHIA has developed several key HIA work products that have helped to expand and refine health impact assessment. 3. The organisation faces several challenges in ensuring its appeal to a wide audience and maintaining long term sustainability.