Increasingly, program managers are incorporating existing standardized tests as part of outcome evaluation. This article identifies guidelines for selecting and using standardized measures following addictions treatment. The principles identified in this context, however, are not only applicable to addictions treatment evaluation but also to the use of standardized measures in outcome evaluation of health programs generally. These guidelines cover eight basic criteria for selecting outcome measures: validity, sensitivity to measuring change, suitability for type of clients in the program, acceptability, clinical usefulness, ease of administration, scoring, and low cost. The article also discusses uses of outcome data, comparison of monitoring client outcomes to other forms of evaluation, and some practical issues related to using standardized outcome measures, including selecting what to measure and interpreting results.