In 1989, Edward Witten discovered a deep relationship between quantum field theory and knot theory, and this beautiful discovery created a new field of research called Chern-Simons theory. The 20-year anniversary of Witten's discovery provided an opportunity to bring together researchers working in Chern-Simons theory for a meeting, and the resulting conference included many of the leading experts in the field. This volume presents several original research articles, including another monumental paper by Witten that is sure to stimulate further activity in this and related fields.