The paper describes how parametric systems have been used to help students bridge from conceptual design to descriptive results. Specifically, it describes projects set in two cities, Hong Kong and Melbourne, to address substantive urban design issues and illustrate that the approach is not scale or culturally bounded. The project undertaken in Hong Kong establishes interdependency models for dense urban structure and examined urban systems that contribute positively to their contextual setting. Parametric models were used to develop diagrams of site potential through models of air movement, light and sun exposure, in particular addressing air quality in one of the most polluted places in Hong Kong. The Melbourne case studies examine urban systems as self-organising systems. In these, the case studies identify parameters that determine two patterns: material pattern of the city and cognitive pattern of the city. The paper illustrates the use of a parametric system as a diagramming tool to explore urban propositions from an urban system.