This book is the proceedings of the conference "Arrangements of Hyperplanes" held in August 2009 as the 2nd MSJ-SI (Mathematical Society of Japan - Seasonal Institute.) The modern study of arrangements of hyperplanes started in early 1980s. Since the object to study is simple (just a finite set of hyperplanes), there are various mathematical approaches to arrangements including algebra, topology, combinatorics, singularities, integral systems, hypergeometric functions and statistics. Since numerous world-leading experts gave talks in the 2nd MSJ-SI, this book covers many pioneering approaches and new topics in the theory of arrangements as well as indispensable classical results. The book is recommended to any researcher or graduate student who is interested in arrangements of hyerplanes.Published by Mathematical Society of Japan and distributed by World Scientific Publishing Co. for all markets except North America