Presented in two parts, this first comprehensive overview addresses all aspects of energetic ion irradiation of polymers. Earlier publications and review articles concentrated on selected topics only. And the need for such a work has grown with the dramatic increase of research and applications, such as in photoresists, waveguides, and medical dosimetry, during the last decade. The first part, Fundamentals of Ion Irradiation of Polymers covers the physical, chemical and instrumental fundamentals; treats the specific irradiation mechanisms of low- and high-energy ions (including similarities and differences); and details the potential for future technological application. All the new findings are carefully analyzed and presented in a systematic way, while open questions are identified.