The need for organizational innovation as a means of improving health-care quality and containing costs is widely recognized, but while a growing body of research has improved knowledge of implementation, very little has considered the challenges involved in sustaining change - especially organizational change led 'bottom-up' by frontline clinicians. This study addresses this lacuna, taking a longitudinal, qualitative case-study approach to understanding the paths to sustainability of four organizational innovations. It highlights the importance of the interaction between organizational context, nature of the innovation and strategies deployed in achieving sustainability. It discusses how positional influence of service leads, complexity of innovation, networks of support, embedding in existing systems, and proactive responses to changing circumstances can interact to sustain change. In the absence of cast-iron evidence of effectiveness, wider notions of value may be successfully invoked to sustain innovation. Sustainability requires continuing effort through time, rather than representing a final state to be achieved. Our study offers new insights into the process of sustainability of organizational change, and elucidates the complement of strategies needed to make bottom-up change last in challenging contexts replete with competing priorities.