THIS BOOK FOR POLICYMAKERS AND THEIR STAFFS DISCUSSES JUST WHAT A LARGE-SCALE MODEL CAN AND CANNOT DO, HOW THE TASK OF CONSTRUCTING A MODEL SHOULD BE APPROACHED, HOW DEVELOPMENT CAN BE SPREAD OVER A VARIETY OF TASKS SO THAT THE FINAL COST IS SHARED BY A NUMBER OF DEPARTMENTS, AND AND THE TERMINOLOGY USED BY THE COMPUTER SOFTWARE EXPERTS WHO WILL BE CALLED UPON TO DEVELOP THE MODEL. A STEP-BY-STEP APPROACH TO MODEL BUILDING AND VALIDATION IS PRESENTED IN NONTECHNICAL LANGUAGE. ONE CHAPTER DISCUSSES MEANINGFUL IMPLEMENTATION OF THE MODEL. WAYS IN WHICH A MODEL CAN BE USED BY MORE THAN ONE DEPARTMENT ARE ALSO EXAMINED. ANOTHER CHAPTER PRESENTS EXCERPTS WRITTEN BY EXPERTS IN THE FIELD COVERING SUCH TOPICS AS PREDICTING BEST WITH IMPERFECT DATA, FAILURE OF TRANSPORTATION MODELS, DOCUMENTATION, MODEL USE, MODEL POLICIES, MANAGEMENT OF A MULTIDISCIPLINARY RESEARCH PROJECT, BUILDING A MAN-MACHINE MODEL, A SPECIFIC METHODOLOGY FOR BUILDING MODELS, A METHODOLOGY FOR MODEL EVALUATION, ENVIRONMENTAL PROTECTION AGENCY MODEL DOCUMENTATION STANDARDS, MODELING SINS AND GUIDELINES, AND THE USE OF URBAN MODELS. EACH OF THESE EXCERPTS IS A COMPLETE SCIENTIFIC PAPER, CONDENSED TO BE MORE READABLE TO THE LAYPERSON. THE FIRST APPENDIX PRESENTS A BRIEF DESCRIPTION OF EACH OF NINE SOCIAL SYSTEMS MODELS, ALL IN USE AT THE TIME OF WRITING, WHILE THE SECOND DETAILS DATA NEEDS FOR EACH OF THESE NINE MODELS, SOURCES OF THE DATA, OUTPUTS, PROBLEMS WITH THE MODEL, USEFULNESS, AND TRANSFERABILITY. THROUGHOUT THE DISCUSSIONS, THE STRENGTHS AND LIMITATIONS OF THE MODELS FOR POLICY EVALUATION ARE STRESSED. THE BOOK CONTAINS CHARTS AND TABLES COMPARING VARIOUS MODELS AND AN EXTENSIVE INDEX.