The purpose of this paper is to review some of the methods used for the impact evaluation of Demonstrator-Developer projects and to promote the meta-analysis approach. Four examples of attempts to collect and analyze impact data from adopters are presented, one of which used the meta-analysis approach. In this example, each adopter collected pre and post data using instrumentation specified by the parent project. The results were used to compute an effect size (a standardized growth measure) for each project using the performance of the control group in the original project. Using this approach, one not only is able to get an estimate of the effectiveness of each separate adoption, but the data can easily be aggregated for an estimate of the effectiveness of the parent project. (BW)