This issue of New Directions for Evaluation explores evaluation within the context of nonprofit organizations. In recent years, many have observed that nonprofit organizations are under increasing pressure to demonstrate their effectiveness and document their program outcomes, as the current political and funding environment continues to stress the importance of accountability and measuring performance. Foundations, government agencies, and other funders are asking nonprofit organizations for more evaluation and performance measurement data. Yet, most nonprofit organizations continue to struggle with these demands, and many lack the capacity to implement evaluation and performance measurement in comprehensive or meaningful ways.