We present numerical results on the exposure of Implantable Medical Devices to electromagnetic fields produced by radio communication systems in common usage scenarios. Initially, a theoretical model based on simple formulas provides an order-of-magnitude assessment to identify critical cases that require further analysis. Subsequently, full wave analysis is carried out considering the detailed composition of the body of the patient bearing the Implantable Medical Device (IMD), the source of electromagnetic field, and the characteristics of the IMD.