St. Joseph's Healthcare Hamilton (SJHH) supports a grassroots green team, called Environmental Vision and Action (EVA). Since the creation of EVA, a healthy balance between corporate projects led by corporate leaders and grassroots initiatives led by informal leaders has resulted in many successful environmental initiatives. Over a relatively short period of time, environmental successes at SJHH have included waste diversion programs, energy efficiency and reduction initiatives, alternative commuting programs, green purchasing practices, clinical and pharmacy greening and increased staff engagement and awareness. Knowledge of social movements theory helped EVA leaders to understand the internal processes of a grassroots movement and helped to guide it. Social movements theory may also have broader applicability in health care by understanding the passionate engagement that people bring to a common cause and how to evolve sources of opposition into engines for positive change. After early successes, as the limitations of a grassroots movement began to surface, the EVA team revived the concept of evolving the grassroots green program into a corporate program for environmental stewardship. It is hard to quantify the importance of allowing our staff, physicians, volunteers and patients to engage in changes that they feel passionately about. However, at SJHH, the transformation of a group of people unsatisfied with the organization's environmental performance into an 'engine for change' has led to a rapid improvement in environmental stewardship at SJHH that is now regarded as a success.