Broadly conceived, social impacts refer to all changes in the structure and functioning of patterned social ordering that occur in conjunction with an environmental, technological, or social innovation or alteration. Departing from the usual cost-benefit analysis approach, a new methodology proposes conducting social impact assessment grounded in the theoretical perspective of human ecology. Empirically, the methodology uses quality of social life indicators (50 community characteristics categorized under the headings of demography, economy, social structure, public services, and social well-being) that are measured with objective data, weighted according to subjective value judgements, and combined into factor indexes. The principal benefit of this methodology is that it enables social scientists to use dynamic system modelling to predict the most likely impacts of any specified innovation. Although this methodology still requires refinement and testing, its main features can be of practical use to social researchers and planners in measuring the actual effects of ongoing programs or projects and for forecasting the likely consequences of proposed policies or developments. (NEC)