This paper looks at the use of a System Dynamics model to support the development of a strategy to address diabetes in Manukau, a large multi-cultural city sitting on the southern border of New Zealandís largest city, Auckland. The paper describes the development of the model, from a simple, high-level conceptual framework to a computer simulation used to test a range of policy scenarios. As part of a major project undertaken by the Counties Manukau District Health Board, the model was developed with a team comprising clinicians across the spectrum from public health, through primary and secondary care. The model has been useful to inform thinking and develop a broader, system-wide understanding of diabetes and the strategies needed to address it.