The document describes NIDOS, a network of 91 international development organizations in Scotland. It discusses NIDOS' effectiveness programme since 2009 which included consultations to develop a self-assessment tool to help members evaluate their effectiveness. The tool, launched in 2010, is based on five principles of accountability, sustainable development, learning organizations, governance and efficiency, and partnerships for social justice. It provides benchmarks and self-assessment questions under each principle to help organizations document good practices, identify areas for improvement, and develop action plans. The aim is to help organizations strengthen their work and share approaches to effectiveness. A link to try the online tool is provided.