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The formal aspects of Forrester's general procedure and some of the substantive assumptions incorporated in his model are discussed. The evaluation is based on the methodological dictum that the status of a model's predictions should be assessed in terms of the assumptions that determine these outcomes. In order to identify the control structure of Forrester's model, the implications of variations in the following parameters or structural assumptions are studied: the basic transition rates in the sectors industry and housing; the multipliers that relate to the competition for scarce land; an alternative conception of industrial regeneration; the conditions governing pressures and flows in the population sector that induce an overall "converter" cycle; and the underemployed/labor job ratio and its concomitants. The latter two sets of conditions are reviewed in terms of their relationship to the general development of industry. The situation of the underemployed is analyzed and their existence set in relation to general features of the present stage of industrialization. The particular closed-system conceptualization that underlies the model is discussed, and an assessment of its adequacy to the problem is presented.