Abstract: This research mainly focuses on antennas for implantable medical devices in a human body and subsequently includes topics related to exterior telemetry links. Antennas inside/outside a human body are applicable to hyperthermia and telemetry. To make practical use of antennas for the medical applications, resonance characteristics of the antennas and their radiation signature outside the body are evaluated throughout this research. Most importantly, the antennas are designed with an in-depth consideration given to its surrounding environment. The spherical dyadic Green's function and finite difference time domain (FDTD) codes are applied to analyze the electromagnetic characteristics of dipole antennas and low profile patch antennas inside/outside a human body. Low-profile antennas with superstrate dielectric layers are initially designed for medical devices implanted in the chest of the human body using the FDTD simulations and measured in tissue-simulating fluid. The performances of the designed low-profile antennas are estimated in terms of radiation patterns, radiation efficiency, and specific absorption rate (SAR). Maximum available power calculated to characterize the performance of a communication link between the designed antennas and an exterior antenna show how sensitive receivers are required to build a reliable telemetry link. By applying planar inverted F antenna (PIFA) structures, meandered-shaped and spiral-shaped implanted antennas are developed on an implantable medical device. The radiation characteristic comparison between two different shaped antennas shows spiral radiator is more appropriate for wireless telemetry links. For parametric studies related to implanted antennas, it is evaluated how much the radiation performances of the implanted antenna are affected by the skin's thickness and the antenna's location. Electrical characteristics of an electromagnetic bandgap (EBG) structure embedded in dielectric layers are studied to design low-profile loop antennas for exterior wireless links. For diversity applications, dipole and loop radiators are incorporated. The simulated and experimental results show embedded EBG structures are applicable for the low-profile antenna design. To improve the diversity performance of the low-profile dipole/loop (dual) antenna, parasitic elements are introduced in the configuration of the dual antenna.