Major advances in the number, capabilities, and quality of state, national, and transnational databases have opened up new opportunities for evaluators. Both large-scale data sets collected for administrative purposes and those collected by other researchers can provide data for a variety of evaluation-related activities. These include (a) identifying or highlighting issues that invite greater client attention; (b) establishing the plausibility of policy theories of action; and (c) program evaluation. The authors illustrate through examples from the fields of education, social services, and public health both the opportunities provided by higher quality, interoperable data systems and the challenges encountered when using databases to identify issues of concern, test the plausibility of a proposed theory of action, or evaluate an existing program. The authors then explore implications for roles evaluators may need to play to support these uses of databases and for funding and infrastructure to support greater evaluator involvement in program planning and improvement.