SADT™ (A trademark of SofTech, Inc.,Waltham, MA), a hierarchical system description notation, was used to create System Dynamics models. This paper discusses the two SADT model types, data and activity, and their correspondence with System Dynamics patterns. Rules for transforming an SADT data model to a System Dynamics model, semi-automatically, are proposed. This information is then used in a step by step translation from a SADT data model to a System Dynamics simulation model. An example is given showing how the SADT hierarchy enhances the understanding of the simulation model.