The tension between personal privacy and public accountability produces one of the major ethical dilemmas facing behavioral health program evaluators and service system researchers. This article discusses the source of this tension and introduces a research methodology that allows program evaluators to fully and equally respect both ethical principles. This methodology uses contemporary computer and statistical technology in conjunction with aggregated, de-identified information derived from existing databases to provide valid and reliable measures of the performance of treatment programs while it protects the personal privacy of individuals.