Improved experimental techniques in cellular biology, physiology, and other areas of medical/biological research constantly provide us with new information on different biological processes. Our understanding of the complicated interplay among all of these processes is making modest progress. We need a systems-oriented modeling approach to put the pieces together and test if they are mutually consistent. With its emphasis on material conservation conditions, feedback regulation, non-linear interactions, and well-defined time scales, System Dynamics represents a unique approach to the modeling of dynamic processes in living systems. The System Dynamics Group at The Technical University of Denmark has been involved in this type of research since the 1970ís, and is now coordinating one of EUís most significant efforts in Systems Biology (Biosimulation Ė A New Tool in Drug Development) with 40 academic, industrial and regulatory partners. The presentation will discuss the role that System Dynamics can play in the medical and biological sciences. Iíll present examples of dynamical models of physiological processes, starting with a simple model of insulin absorption from the skin. This model has changed the way rapidly-acting insulin is produced today. Iíll also discuss a model of how the individual nephron in the kidney regulates the incoming blood flow and how neighbouring nephrons interact with one another to synchronize their blood flow regulations.