This is a comprehensive reference book on combinatorial designs. It covers all of the most important results in the field as well as the basic ones. These include not only constructions of designs, their properties and existence results but also many examples and applications of combinatorial designs (in cryptography, communication, networking, statistics, testing and many more). The core of the book is in five parts, four of them being devoted to four main classes of combinatorial designs: balanced incomplete block designs, orthogonal arrays and latin squares, pairwise balanced designs and the Hadamard and orthogonal designs. The fifth part contains sixty-five chapters that concern other classes of designs. Each chapter makes references to related topics, many of them naturally crossing the sections. There are two more parts. The first one is introductory, providing an overview of the field and an historical perspective. The last part gives the necessary mathematical and computational background. It is not expected that the book will be read in a sequential way. Hence, to have direct access to relevant topics information is given in an easy-to-access way, often captured in a table indexed by parameters of designs. Moreover, the book is equipped with a large index providing even faster navigation through pages. An extensive bibliography with more than 2200 items can serve as an excellent source of information itself. The book has more than 900 pages (prepared by more than 100 contributors). You will find here an answer to any of your questions about combinatorial designs.