Excerpt from the report Preface: The basic theory underlying the use of systems of simultaneous equations in economic research was developed about 1943. Much of the early literature on this subject assumed a knowledge of higher mathematics and most of the applications of the method were made by research workers who had such knowledge. More recently, descriptions of this general approach that presume only a limited knowledge of mathematics have been published; and the method itself is beginning to be used by research workers who have little or no knowledge of calculus and matrix algebra. This handbook is designed to provide a complete description of the steps involved in the more common types of problems and to illustrate them in a way that will be clear to research and clerical workers who have an acquaintance only with standard methods for handling single equation multiple regression analyses. Some knowledge of determinants and matrices is required for a number of problems, but these aspects are discussed in considerable detail before they are applied.