Jay Forrester's book, Urban Dynamics, calls attention to and relates several important concerns: the complexity of urban environments and problems, and the need for rigorous appraisal and validation criteria and techniques to control policy-oriented research efforts. We investigate each of these concerns. Few books in the social sciences have attracted as many critics as Urban Dynamics. However, none of them has succeeded in producing a concise, thorough, and balanced appraisal of the work. For example, economists view the effort as an affront to established theoretical shibboleths, but uniformly fail to acknowledge both strengths and weaknesses along other important dimensions of an appraisal function; city planners sense in Forrester a kindred spirit, trying to simplify and arrange the world in ways congenial to what planning schools have long preached, but planners also fall to consider more than a select few of the problems created by the work; and policlymakers, to judge by the currency accorded the book by several professional groups, sympathize with several of the policy messages advanced by Forrester, but they understand little more than the stories told in his "wiggly line" graphs. We "evaluate the evaluators," summarize their main arguments concisely, and attempt to reconstruct a better approximation of an appraisal function for consideration and subsequent use on this and similiar efforts. This reconstituted function is then employed to reappraise Urban Dynamics. Particular emphasis is placed on several theoretical deficiencies and more importantly on the technical adequacy of the basic formulation. For example, sensitivity analysis indicates that several key structural relationships and a select few parameters are so critical for the model's behavioral outputs that only minor modifications are capable of producing results quite different than those on which Forrester based his policy interpretations. The paper concludes with a summary of "where we might go from here" addressed to several relevant groups of discipline and operational specialists. Hopefully, this paper summarizes much of the diffuse argumentation and redirects collective and specialized attention to the more important and formidable tasks at hand.