A symposium titled "Polyphosphazenes in Biomedicine, Engineering & Pioneering Synthesis" was held at a recent meeting of the American Chemical Society (ACS) in August 2017 in Washington, DC. The chapters in this book provide a summary of the international contributions reported at that meeting, the purpose of which was to bring together a broad range of topics, research investigators, and representatives from industry to discuss the current status of different aspects of this field.