Extension and advisory services (EAS) play a key role in facilitating innovation processes, empowering marginalized groups through capacity development, and linking farmers with markets. EAS are increasingly provided by a range of actors and funded from diverse sources. With the broadened scope of EAS and the growing complexity of the system, the quantitative performance indicators used in the past (for example related to investment, staffing or productivity) are no longer adequate to assess the performance of EAS systems. This operational guide meets the longstanding demand for guidance on undertaking such a comprehensive assessment of national EAS systems. It provides detailed directions on how to organize the entire process, from preparation to implementation and consolidation. Its use will help identify gaps and entry points for targeting investments and realigning policies for transforming EAS.