This chapter focuses on three main topics. The first aims to provide an explanation of the principles of health technology assessment (HTA) and its familiar role in determining coverage of healthcare provision. Second, we discuss the growing contribution of HTA in the development and translation of medical devices introducing what we term "development-focused HTA"(DF-HTA). We set out the role of DF-HTA in identifying needs, assessing the potential of technologies in development, aiding design, and tailoring evidence generation activities. Finally, we outline the challenges of development and assessment presented by medical devices distinguishing large capital items, point of care devices, diagnostics, implantables, and digital devices. Each category of device has its own set of challenges for developers and HTA analysts alike. Challenges include a complex licensing and regulation environment, short lifespan and incremental improvement, difficulties in generating clinical evidence, the importance of contextual factors (e.g., how the device will be used and by whom), patient and clinician acceptance, and the indirect health benefit from diagnostic devices.