Abstract: In recent years, local government land use planning practices have evolved from conventional land use planning to include integrated urban growth and infrastructure management approaches. Urban growth models are increasingly being used to inform the decision-making process and infrastructure planning practice. However, models tend to be non-market based and generally "once-off" applications with a single purpose, rather than dynamic applications that render ongoing planning support. As a consequence, management support and the use of these models by planners remain marginal. UrbanSim is a software-based model system that treats urban development as the interaction between market behaviour and government action and has been under development since the late 1990s. A number of papers describing the application and inherent workings of UrbanSim have appeared in the formal and grey literatures, but the way in which UrbanSim gets embedded in planning practice has remained largely ignored and poorly understood. Based on data from a case study implementation of UrbanSim in Logan City, this paper describes how UrbanSim is applied for use in Australian planning practice. Summary outputs of an UrbanSim model are provided, but the main focus of this paper is how the model system and outputs are perceived by planning actors. Findings suggest that a technical focus is insufficient to improve the implementation of the model. The key obstacles are centred more towards "soft issues" such as a lack of transparency and poor connections to the planning process. The paper concludes with a discussion that offers potential remedies for these shortcomings.