This paper addresses the question of whether administrative data that are collected for performance monitoring purposes can be used for program evaluation. It argues that under certain circumstances, such data can be used. In particular, data from the state of Washington are used to examine the effectiveness of services provided to adults under the Workforce Investment Act (WIA). The general theme of an emerging literature on techniques for nonexperimental evaluations of social programs is that many different techniques have appropriate asymptotic properties. A contribution of this paper is to examine the sensitivity of net impact estimators to various estimation techniques. Virtually all of the techniques yielded estimates of positive labor market impacts for both men and women. Men had earnings gains on the order of 10 percent that resulted mainly from increased employment rates. Women had larger estimated earnings gains—on the order of 20 to 25 percent—that emanated from increased employment and increased wages or hours. A second purpose of the paper was to provide principles that policymakers and program administrators should apply when considering evaluation results.