This book introduces the reader to an area of elementary particle physics which has been the subject of intensive research in the past two decades. It provides graduate students with the basic theoretical background on quantum gauge field theories formulated on a space-time lattice, and with the computational tools for carrying out research in this field. The book is a substantially extended version of the first edition which appeared in 1992. Much effort has been invested to present the material in a transparent way, and in exemplifying subtle points in simple models. The material covered should enable the reader to follow the vast literature on the subject without too much difficulties. Hopefully the book will motivate young physicists to carry out research in this area of elementary particle physics.