Information systems (IS) are situated in and representations of business and organizational domains. Conceptual models of the real world serve as tools for understanding the business domain. Conceptual modelling is thus an important first step in any IS development project. As no language has been generally accepted for conceptual modelling, researchers have proposed extending the use of widely accepted object-oriented software design languages such as UML for this purpose. A major problem with this is the fact that such languages possess no real-world business or organizational meaning— that is, it is unclear what the constructs of such languages mean in terms of the business. This chapter discusses how such meaning can be assigned to languages like UML. It provides an example that demonstrates the differences between a software design model and a conceptual model in UML. This chapter shows that UML is suitable for conceptual modelling but that the modeller must take special care not to confuse software aspects with aspects of the real world being modelled.