Appropriately for a book having the title "Computer Simulation Methods in Theoretical Physics", this book begins with a disclai mer. It does not and cannot give a complete introduction to simu lational physics. This exciting field is too new and is expanding too rapidly for even an attempt to be made. The intention here is to present a selection of fundamental techniques that are now being widely applied in many areas of physics, mathematics, chem istry and biology. It is worth noting that the methods are not only applicable in physics. They have been successfully used in other sciences, showing their great flexibility and power. This book has two main chapters (Chaps. 3 and 4) dealing with deterministic and stochastic computer simulation methods. Under the heading "deterministic" are collected methods involving classical dynamics, i.e. classical equations of motion, which have become known as the molecular dynamics simulation method. The se cond main chapter deals with methods that are partly or entirely of a stochastic nature. These include Brownian dynamics and the Monte Carlo method. To aid understanding of the material and to develop intuition, problems are included at the end of each chapter. Upon a first reading, the reader is advised to skip Chapter 2, which is a general introduction to computer simUlation methods.