Worldwide, extension and advisory service (EAS) systems have undergone reforms since the 1990s. However, the reforms of the last two decades in many countries have largely failed, as there has not been significant increase in accountability, efficiency, empowerment or impact. To fill this gap, this document, based on a systematic and extended literature review, delves into public EAS systems in developing countries, with a special focus on smallholder farming and institutional reforms. To begin with, it reviewed the status quo of global EAS systems in terms of institutional change and typologies and regional characteristics of EAS systems based on the analysis of 80 countries. This is followed by discussions on issues related to human resources, mandates, financial resources, infrastructure, and policy environment. The discussions are illustrated with six country case studies. Then, the document analyses the major challenges faced by institutional reforms in developing countries regarding accessibility, accountability, affordability, adaptability, sustainability, and coordination. Next, the document summarises the experience and lessons-learnt from EAS reforms across the developing countries. Finally, based on the previous discussions, it gives recommendations on strengthening and reforming public EAS systems.