We are considering the challenges that regulators face in approving modern medical devices, which are software intensive and increasingly network enabled. We then consider assurance cases, which o er the means of organizing the evidence into a coherent argument demonstrating the level of assurance provided by a system, and discuss research directions that promise to make construction and evaluation of assurance cases easier and more precise. Finally, we discuss some recent trends that will further complicate the regulatory approval of medical cyber-physical systems.