The Wellesley Urban Health Model simulates alternative scenarios to help explain the impact of interventions on poor health outcomes such as chronic disease rates, disability rates and mortality rates. The model also gives insight into how much and how quickly interventions can reduce mortality and morbidity. The Wellesley Institute’s goal is to provide a tool that will allow us, our stakeholders and other policy-makers to ask “what if” questions about policy interventions and as a result,guide us to useful research questions and potential solutions for complex population health problems.